Assurance is one of the five important dimensions of SERVQUAL. Although it has been widely used to measure customer perceptions in regard to service trustworthiness during service delivery in various service industries, there are several arguments regarding assurance dimension in the spa industry. First, several scholars criticised the unclear definition of assurance as it is interpreted differently by service providers and customers (Eastaughffe 2018; Llosa et al. 1998; Ladhari 2009; Olorunniwo et al. 2003). According to Parasuraman et al. (1988 23), assurance is defined as the “knowledge and courtesy of employees and their ability to inspire trust and confidence”. Knowledge and courtesy are clearly important elements of the assurance dimension. However, the phrase ‘their ability to inspire trust and confidence’ may be interpreted differently by different parties in service industries, including the spa industry. For example, scholars often limit their measurements to a small number of items such as the knowledge and courtesy of employees, spa cleanliness, and customer security (Chieochankitkan and Sukpatch 2014; Sangpikul 2019; Snoj and Mumel 2002; Vryoni et al. 2017). Measuring only a few items may not reveal the complete picture in regard to customer perceptions of assurance in the spa industry.

Second, the in-depth analysis of literature revealed some variation in the interpretation of the reliability and assurance dimensions in regard to spa service quality. For example, several studies interpret spa employees’ knowledge and professionalism (skills, competence) as key elements of reliability (e.g. Lo et al. 2013; Sangpikul 2019; Snoj and Mumel 2002) while other studies include the knowledge and skills of therapists as essential elements of assurance (e.g. Chieochankitkan and Sukpatch 2014; Silvestri et al. 2017; Warakunsirisak and Watakit 2020). Moreover, certain studies focus only on the physical environment such as the cleanliness of spa venues and facilities (Lo et al. 2015). The variation in the interpretation may occur due to the ambiguity in the definition of assurance as earlier mentioned.

Third, assurance is a key issue for the spa industry due to dynamic changes in the service environment. In particular, during COVID-19, research indicates that customers place more importance on health and safety when selecting a service provider (Japutra and Situmorang 2021; Jiang and Wen 2020). The lower the degree of health risk perceived by the consumer, the greater their intention to resume their consumption of hospitality and tourism services (Peco-Torres et al. 2021), which includes spa services. Consequently, service quality attributes in regard to customer concerns on heath safety and hygiene are also increasingly important in the spa industry. Spa managers are required to understand and respond to the changing perceptions of customers in order to deliver the expected services during COVID-19. In this regard, new research is needed to update the existing literature in order to better understand the role of assurance in the current situation.

To fulfil the research gaps, this research, therefore, employs a qualitative exploratory methodology to examine three different sources of information to acquire a better understanding of the assurance dimension of SERVQUAL in the spa industry by focusing on spas in Bangkok, Thailand. The results of the study are expected to yield new findings and offer a deeper understanding of the assurance dimension of SERVQUAL in the current situation, which have both academic and practical implications.

1.1 Spa industry in Thailand

Thailand is a well-known tourist destination for wellness tourism in Asia (Hashemi et al. 2015; Sangpikul 2022). Wellness tourism is generally referred to as travel with the aim to maintain or enhance ones’ well-being in mind and body through the experience of health-promoting activities or services, for example, day spas, bathing facilities, fitness centres, and spa resorts (Fernandes and Fernandes 2013). Spas are related to wellness tourism because they aim to help to promote the physical and mental well-being of tourists (Dimon 2013). In Thailand, a spa generally refers to water-based services that offer health-related services such as body massages/relaxation, facial & skin treatments, and additional services such as saunas and exercise courses (Hashemi et al. 2015; Sangpikul 2022). Among the various types of spa, day spas are the most popular in Thailand. In general, a day spa is a service-based business that offers a variety of health-related services to day-use clients. It is open to the public and offers a la carte spa services to customers who can enjoy a number of individual treatments or a full day treatment (Wisnom and Capozio 2012). Bangkok is the most well-known destination for day spas in Thailand for international tourists with hundreds of spa service providers located throughout the city (Sangpikul 2022).

1.2 Spa service quality and its assessment

Service quality is an evaluation of how well a delivered service meets customer expectations (Parasuraman et al. 1988). It is an important measurement tool for service industries (including spa establishments) to understand how well their services meet customer expectations (Lo et al. 2015; Sangpikul 2019). Understanding service quality can assist spa managers to deliver superior services to meet customer expectations, contributing to customer satisfaction, word-of-mouth communication, and loyalty (Memarzadeh and Chang 2015; Lo et al. 2015). One of the well-known instruments to access service quality is SERVQUAL (Parasuraman et al. 1988). It is a global instrument aimed to measure consumer expectations and perceptions of service performance based on five dimensions: 1) reliability, 2) empathy, 3) assurance, 4) responsiveness, and 5) tangibles. Each dimension is defined as follows (Parasuraman et al. 1988, 23).

Reliability: the ability to perform the promised service dependably and accurately

Among the five dimensions, assurance is one of the most criticised because of its ambiguity and the variations of interpretation in service literature as previously mentioned. In addition, in-depth analysis also reveals that there are sub-categories of the assurance dimension in regard to spa service quality as identified in literature. For instance, several spa studies measured the assurance dimension in terms of employee knowledge and courtesy (Chieochankitkan and Sukpatch 2014; Sangpikul 2019; Vryoni et al. 2017) while other studies described assurance in terms of the physical environment such as venue cleanliness, customer security, and spa facilities. (Lo et al. 2015; Snoj and Mumel 2002). Moreover, literature also suggests other attributes which may inspire customer trust and confidence during service delivery, for example, the quality of spa products (Lo et al. 2015), the skill of spa therapists (Sangpikul 2019; Silvestri et al. 2017), employees’ problem-solving skills (Snoj and Mumel 2002), employee hygiene (Sangpikul 2022), customer privacy (Sangpikul 2019), and secure transactions (Chieochankitkan and Sukpatch 2014).

The literature suggests that assurance in relation to spa service quality may not only involve employee knowledge, courtesy, and the physical environment, but may also include other attributes regarding employee competence (e.g. skills, experiences), product attributes (e.g. quality of spa products), and certain processes (e.g. secure transactions). This suggests that assurance in the spa industry may include sub-categories or sub-dimensions, and seems to be more complicated than the other SERVQUAL dimensions due to its varied attributes. A complete picture in regard to the assurance dimension in the spa industry has not yet been obtained.

Content analysis is employed as the main method to analyse the data (secondary data, expert discussions, and customer interviews). This method is suitable for qualitative studies by providing a systematic and objective means to make valid inferences from verbal or written data in order to describe specific phenomena (Downe-Wamboldt 1992 cited in Salem et al. 2022).The current study employs a directed content analysis to analyse the data. Hsieh and Shannon (2005) identified three methods of content analysis: conventional, directed, and summative approaches. Directed content analysis is employed in this study as it uses theory and relevant research findings as a framework for data analysis. Its goal is to validate or conceptually extend a theoretical framework. In this study, Parasuraman et al. (1988)’s definition of assurance is employed as an initial framework to focus the issues related to assurance attributes in regard to spa service quality. For example, any content (either customer reviews or interviews) related to the knowledge and courtesy of employees as well as their ability to inspire customer trust and confidence during service delivery are assumed to be related to assurance, and are thus categorised into sub-themes and major themes accordingly. All data collection and analyses were performed by the researcher, given the small scale of the study which examines only a single dimension of SERVQUAL. Data were collected during November - December 2021.

The first method involves the analysis of secondary information from the literature and customer reviews. This method was employed to explore related literature as well as to present what has been documented and what hotel customers actually said about assurance, thereby helping to identify gaps in the literature. To analyse the literature, academic databases (e.g. Scopus and ScienceDirect) and search engines (e.g. Google Scholar) were employed. Key words for article searches were, for example, ‘spa and service quality’ and ‘spa and SERVQUAL’. Only studies related to spa service quality and the research objective were included in the analysis (a total of 15 articles). In order to analyse customer reviews, data were collected from a popular review website, TripAdvisor, as suggested by the literature (Memarzadeh and Chang 2015; Sangpikul 2019). Past studies indicate that many spa customers share or post their experiences regarding assurance issues on TripAdvisor (Sangpikul 2019). Both positive and negative reviews, over a 1-year period, were examined to ensure a thorough investigation of assurance-related issues. The online reviews about day spas in Bangkok were examined because the largest number of registered day spas are located in Bangkok. The list of day spas is available from the Ministry of Public Health which is in charge of promoting wellness businesses in Thailand. According to the Ministry of Public Health (2020), there were 114 registered spa establishments in Bangkok. Only spas with the required information available on TripAdvisor were included in the analysis. Finally, a total of 95 spas were examined by collecting reviews or statements in regard to assurance attributes of spa services. Collecting many reviews from various service providers helps to enhance the reliability of the study (Sangpikul 2022).

The second method involves discussions (semi-structured interviews) with spa managers/supervisors to acquire deeper insight into assurance attributes. Being an exploratory study with certain limitations during COVID-19, approximately 20% of spa establishments in Bangkok were randomly selected from the lists, and invitation letters were sent to them. At the initial invitation stage, only four spa establishments agreed to participate in the interviews. However, the researcher invited approximately 20% more spa establishments until there were a total of eight spa establishments that agreed to take part in the online interviews (with audio recording). Before the interviews, all participants were informed about the topic and research objectives. Each interview took around 30-35 minutes. The interview questions were, for example, ‘What do you understand by the term service quality and how is it related to the spa services?’, ‘Could you please indicate which attributes of your services can enhance customer trust and confidence during service delivery?’, and ‘In the current situation of COVID-19, what attributes of your services can encourage customer trust when using spa services?’.

The third method involves interviews with spa customers with the aim to acquire deeper insight based on customer experience. The target customers were those who had used spa services at least two times during the past 12 months to ensure that the respondents had sufficient experience of spa services. The researchers could stop the interview when there was sufficient or saturated data, as no additional information could be obtained (Alam 2021, Mariampolski 2001; Morse 2007). In this study, the researcher decided to stop collecting data from 25 foreign customers (17 females and 8 males from 8 spa establishments) when there was sufficient information and nothing new was revealed (Cohen et al. 2000). Data collection was conducted at spas in Bangkok with permission from spa managers. All participants were informed about the research topic and objectives and permission was requested to use audio recording for data analysis purposes. The participants were asked about service quality in general, and more specifically about assurance in the spa industry. The interview questions were, for example, ‘How do you judge the quality of spa services?’, ‘When you are spa customers, what service attributes can enhance your trust or confidence when using spa services?’, and ‘What factors can enhance your trust or confidence when using spa services during COVID-19?’.

Data analysis was based on literature (Salem et al. 2022; Suttikun et al. 2018). For example, the researcher transcribed the interviews and the data were coded based on words, phrases, and sentences in the texts. Codes with similar meaning were categorised and labelled. The data were subsequently classified into sub-themes, and major themes (categories) in regard to spa assurance attributes. Finally, data interpretation was performed to obtain an overall understanding of the findings.

3.1 The analysis of related literature and online reviews

Table 1 presents the analysis of related literature and customer reviews with the aim to analyse what has been documented in the literature and what customers actually said about trust and confidence during service delivery. This analysis helps to identify both gaps in existing literature and new findings. The information from two sources was then analysed together with the interview findings to determine a spa assurance framework.

Table 1:

Related literature (what is documented)	Customer reviews (positive & negative)	New findings (what is undocumented)	Summary of themes and items
1.1 Quality of spa products (Lo et al. 2015)	“Facial was wonderful, they used the best products on my skin” “The aroma smell is artificial and cheap quality” “Avoid facials as they do not seem to use good products to provide this treatment”	-	Theme 1 -Quality of spa products
2.1 Knowledge and skills (Chieochankitkan and Sukpatch 2014; Silvestri et al. 2017; Vryoni et al. 2017) 2.2Employee courtesy and friendliness (Chieochankitkan and Sukpatch 2014; Silvestri et al. 2017; Vryoni et al. 2017) 2.3 N/A 2.4 N/A	“Staff was knowledgeable and recommended a suitable massage for me” “The massage was great and beyond my expectation. Our therapist was both very skilful and experienced” “I did not know how the spa trains their employees. The staff at the reception cannot tell me the difference and the ingredients of my facial treatment I chose” “So disappointed on the masseuse skill, compared to outside massage, poor quality” “I got a female masseuse, she was extremely rude, (did) not smile, and rush(ed) to finish her work. I did not enjoy my massage this time” “Therapist was very nice and polite” “I would like to thank the entire spa staff for their warm welcome” “Therapists here can speak and understand English well. I have no problem with the massage and foot spa” “The service was poor. I can't believe the therapist was unable to speak English, so (there was) a bit (of a) communication breakdown” “Therapists wear surgical masks (at) all times, helping protect customers and themselves” “I am not sure if the therapist washed her hands properly. She just finished her phone call and (came) back to massage my face”	- - service communication employee hygiene	Theme 2 - Knowledge -Courtesy, friendliness - Skills/competence - Communication - Personal hygiene
3.1 Customer security (Lo et al. 2015; Sangpikul 2019; Snoj and Mumel 2002; Vryoni et al. (2017) 3.2 Customer privacy (Sangpikul 2019) 3.3 Cleanliness (Lo 2015; Sangpikul 2019) 3.4 N/A	“There were no lockers, personal belongings were in the same room, be careful” “We got a family room for 4 of us. The therapists started talking to one another and laughing, constantly, so (we were) annoyed. We wanted to have a massage and to relax not to hear their talking and laughing” “We had a private room for the two of us, which was clean and well maintained” “Treatment room is super clean, along with all other sanitized amenities and other equipment” “Towels are smelly and some spots on it” “Spa room and equipment here is above average” “Air-con is very old, and there is leaking into my bed”	- - - Facility maintenance	Theme 3 - Customer security - Customer privacy - Cleanliness - Maintenance
4.1Secure transactions (Chieochankitkan and Sukpatch 2014) 4.2 N/A	N/A “I am impressed with the service and the practice of health and safety protocol during Covid-19” “This spa has a good practice of screening customers before giving the treatments like asking (for) your information, (doing a) temperature check, hand sanitiser, and they also gave a free facemask”	- Covid-19 prevention protocol	Theme 4 - Secure transactions -COVID-19 prevention practices

Table 1 shows that there is still limited literature to fully understand spa assurance as several new items were identified. These items may be related to customer trust during service delivery, for example, service communication, employee hygiene, facility maintenance, and process/practice issues. The findings suggest that the existing literature is inadequate to thoroughly understand customer perceptions on spa assurance attributes in the current situation. The common items found in literature and the newly-identified items were categorised into four themes: product features, employee characteristics, physical factors, and process issues. Primary data were also obtained through expert discussions and customer interviews to supplement the secondary data findings, which is described in the following section.

3.2 Discussions with spa experts and customer interviews

Table 2 presents a summary of the discussions with spa managers and customers to identify additional findings in regard to assurance attributes. Generally, spa managers/supervisors have some knowledge about service quality or SERVQUAL. Most of them had heard this term before in undergraduate programs or at spa trainings. Most spa establishments have questionnaires to survey customer satisfaction related to service quality in regard to several issues, for example, the friendliness and courtesy of receptionists, the skill of therapists, understanding customer needs, and the cleanliness of treatment rooms & facilities. However, most spa managers are unlikely to understand which items are relevant to a particular service dimension of SERVQUAL. In this regard, the researcher briefed them about the concept of service quality, and SERVQUAL. The discussions were focused on spa service provider’s ability to inspire customer trust and confidence during service delivery. All participants provided useful information about such issues which is summarised in Table 2. The most common issues were, for example, employee knowledge, courtesy, spa cleanliness and customer security while new items identified from the discussions involved product safety, staff hygiene, maintenance and safety of equipment/facilities, and COVID-19 measures.

Table 2:

Participants	Findings (common items)	Findings (new items)
Discussions with spa experts	- quality of spa products - employee knowledge & skills - employee courtesy & friendliness - spa cleanliness and hygiene - customer security	- product safety - staff hygiene - maintenance and safety of equipment/facilities - practices of COVID-19 protocol
Interviews with customers	- quality of spa products - employee knowledge and courtesy - spa cleanliness and hygiene - protection of customer information and provision of secure transactions	- product safety - staff hygiene - staff honesty - maintenance and safety of equipment/facilities -practices of COVID-19 measures

Some interesting information was also obtained from customer interviews. Almost all customers indicated that they did not really understand the details of service quality but they knew what made them happy and come back. Generally, if a spa establishment asks them to evaluate the quality of spa services (e.g. employee courtesy, skills of spa therapists, cleanliness of spa rooms), they can answer all of these questions based on their actual perceptions. As the price of spa services is relatively high, most customers indicated that spa service providers should do their best because of the need to trust in the services provided. The common items were, for example, the quality of spa products, employee knowledge & courtesy, spa cleanliness and secure transactions while the new items identified by customers included product safety, staff hygiene, maintenance and the safety of facilities/equipment, and COVID-19 measures in spa establishments.

3.3 Summary and discussion

Based on the analysis of related literature, customer reviews as well as the interviews with spa managers and customers, the overall framework of spa assurance can be classified into four categories: 1) product assurance, 2) staff assurance, 3) physical assurance, and 4) process assurance. Each category has combined both common and new items, and is discussed in the following section. Table 3 summarizes the research findings while Table 4 conceptualises spa assurance dimension and its categories based on the current findings.

Table 3:

Current findings (Tables 1 – 2)	Assurance categories	Final items
Theme 1 -quality of products -product safety	Product assurance	- Quality of products (in-house and retail products) - Product safety (in-house and retail products)
Theme 2 -employee knowledge & skills -employee courtesy & friendliness -problem solving skills -communication skills -personal hygiene -honesty	Employee assurance	- Employee personality (friendliness, courtesy) - Employee competence (knowledge, skills, expertise, problem solving skills) - Communication skills - Personal hygiene - Honesty
Theme 3 -venue cleanliness -equipment hygiene -facility maintenance -faculty safety -customer privacy -customer security	Physical assurance	- Cleanliness and hygiene of spa venue, facilities, and equipment - Maintenance and safety of facilities and equipment - Customer privacy (private service, free of noise disturbance) - Customer security (free of danger/risk, belongings)
Theme 4 -secure transactions -protection of customer information -practices of COVID-19 protocol	Process assurance	- Secure transactions (customer information, online payment, card credit security) - Practices of COVID-19 protocol

Table 4:

Spa assurance categories	Attributes
Product assurance	- Quality of products - Product safety
Employee assurance	- Employee competence - Employee personality - Employee hygiene - Employee honesty - Communication skills
Physical assurance	- Cleanliness and hygiene of spa venue, facilities, and equipment - Maintenance and safety of facilities and equipment - Customer privacy - Customer security
Process assurance	- Secure transactions - Practices of COVID-19 protocol

As shown in Tables 3 & 4, product assurance involves the quality and safety of spa products used for in-house and retail purposes. Whilst staff assurance mainly involves employee competence, their personal characteristics and communication skills, physical assurance is concerned with the cleanliness and maintenance of physical facilities and equipment as well as customer privacy and security. Process assurance is associated with secure transactions and the practices of COVID-19 protocol in spa venues. All categories and items may enhance customer trust and confidence during service delivery in the spa industry.

It should be noted, however, that the existing literature may help to partially validate the current findings due to the limited literature regarding assurance in the spa industry. Product assurance is partially supported by Lo et al. (2015)’s study as they examined only one item regarding the quality of in-house products in the context of hotel spas in China. However, spa managers and customers view quality and safety of spa products as one of the important factors contributing to the trustworthiness of spa services, thereby leading to product assurance. For staff assurance, several studies supported this category as it was included and examined in regard to employee knowledge and skills (Chieochankitkan and Sukpatch 2014; Sangpikul 2019; Silvestri et al. 2017) and employee courtesy (Silvestri et al. 2017; Vryoni et al. 2017). In addition, there are newly identified items, such as service communication, employee hygiene, and employee honesty. Both the common and the new items are related to employee personality and characteristics, and it is appropriate to label them as staff assurance with varied attributes.

In regard to physical assurance, this attribute is an important issue to enhance customer trust and confidence about the physical environment. Past studies measure physical assurance in terms of spa cleanliness (Lo et al. 2015; Sangpikul 2019), customer security (Lo et al. 2015; Snoj and Mumel 2002; Vryoni et al. 2017), and customer privacy (Sangpikul 2019). In addition, new items also include the maintenance and safety of facilities and equipment. Consequently, both the common and the new items help to highlight the importance of physical assurance. Process assurance combines secure transactions and the practices of COVID-19 protocol in spa venues. Process assurance may be partially supported by Chieochankitkan and Sukpatch (2014)’s study in regard to secure transactions while the practices of COVID-19 protocol are newly identified based on the current situation. Both items help to determine process assurance.

In the following section, the findings in relation to SERVQUAL dimensions (reliability, responsiveness, empathy, and tangibles) will be discussed based on the summary of related literature in the spa industry (Lo et al. 2015; Sangpikul 2019; Snoj and Mumel 2002; Vryoni et al. 2017). It aims to explain how the four categories of spa assurance play specific roles in enhancing customer trust during service delivery as well as to indicate that they do not overlap with the four dimensions of SERVQUAL.

In a spa setting, reliability usually refers to the provision of error-free services. This dimension also includes the delivery of suitable treatments to meet customer needs and the provision of promised services (e.g. a 1-hour treatment, not a 50-minute treatment). Reliability is normally focused on employees’ work performance and their responsibilities. It is not related to employees’ personal characteristics like friendliness, courtesy or honesty as these attributes are regarded as staff assurance. In other words, customers should feel confident about getting friendly and courteous employees when they visit spa establishments. Responsiveness is usually associated with employees’ willingness to help customers during service delivery (e.g. spa bookings, service changes, service advice) as well as the provision of prompt service, which is expected by all customers. Empathy is the way employees pay attention to customer needs and the delivery of personalised services. Spa customers may make special requests during the treatments as they may have different concerns or problems about their health or skin issues. They expect spa therapists to deliver an individual service. The tangibles dimension is generally related to the physical environment of spa venues such as relaxing atmosphere, beautiful decoration, and the appearance of facilities/equipment. It is not directly concerned with cleanliness, hygiene, maintenance or security issues because they are included in the physical assurance dimension.

In regard to the four categories of spa assurance, product assurance helps to create customer trust in terms of the quality and safety of spa products. Customers should be confident that the spa products that are used during treatments are of sufficient quality and are safe for their skin and general health. For staff assurance, as the price of spa treatment is relatively high, customers should feel confident that they will be welcomed and served by friendly, courteous, and skilled employees during their visit. At the same time, physical assurance in regard to spa services, for example, venue cleanliness, equipment hygiene & safety, customer privacy, and security is also important. Regarding process assurance, customers require that all their personal information and transactions are secure. In addition, during COVID-19, spa service providers should build customer trust and confidence in the practices of COVID-19 protocol in spa establishments.

4.1 Conclusion

Due to ambiguity in the definition of spa assurance and the need to update spa service quality in the current situation, this research employed a qualitative exploratory study to examine three different sources of information to acquire a better understanding of the assurance dimension in the spa industry by focusing on spas in Bangkok. By employing a content analysis method, the study revealed two major findings. First, the assurance dimension of spa service quality can be sub-divided into four key categories: 1) product assurance 2) staff assurance 3) physical assurance and 4) process assurance. Second, perceived hygiene during the COVID-19 pandemic is integrated into the assurance attributes of spa service quality. The study yields initial findings and advances knowledge on the assurance dimension in relation to spa service quality. It also provides both theoretical and practical contributions to the spa industry based on the current situation.

4.2 Theoretical implications

Firstly, the current findings help to clarify the concept of assurance, and also extend the knowledge of SERVQUAL in regard to the assurance dimension in the spa industry. Previously, assurance had been widely-understood in terms of the knowledge and courtesy of employees as originally defined by Parasuraman et al. (1988). However, the phrase regarding employees’ ability to inspire trust and confidence may be interpreted differently by different parties, causing ambiguity and misinterpretation of assurance in academic work and service measurements as earlier mentioned. Given the current findings, the assurance dimension in relation to spa service quality has been identified and conceptualised into four key categories: 1) product assurance 2) staff assurance 3) physical assurance and 4) process assurance. The new findings help to clarify the concept of assurance in regard to what can inspire customer trust and confidence during service delivery. In addition to the knowledge and courtesy of employees, the assurance attributes in relation to spa service quality also involve product assurance, physical assurance and process assurance. Importantly, the findings associated with COVID-19, for example, employee hygiene, facility and equipment hygiene, and the practices of COVID-19 protocol at spa venues, are integrated into the assessment of assurance to better reflect the current situation. The current study, therefore, advances knowledge on the assurance dimension by yielding findings that allow a better understanding of the assurance attributes, and also make a contribution to service quality literature regarding the conceptual understanding of the assurance dimension in the spa industry. Future studies may apply a similar conceptual method to further examine the assurance dimension in other hospitality and tourism sectors.

Secondly, the current study helps to better understand staff assurance. Previously, the knowledge and courtesy of employees was regarded as the dominant attribute of assurance in most service industries. However, the current study has identified other employee attributes which contribute to customer trust during spa service delivery, for example, skills, competence, employee hygiene, service communication, and honesty. These attributes are related to the employees, who are the key persons to inspire customer trust and confidence during service delivery. The findings yield a better understanding of staff assurance in relation to spa service quality.

Thirdly, the current study revealed that the skills or expertise of spa therapists are essential components of assurance to ensure that customers receive professional services from skilful therapists. The finding helps to clarify the misinterpretation among scholars in regard to the reliability and assurance dimensions as earlier mentioned. Several studies include the knowledge and skills of spa therapists as elements of reliability as opposed to assurance (e.g. Lo et al. 2015; Sangpikul 2019). In fact, the knowledge and skills of spa therapists have been identified as parts of staff assurance based on empirical evidence. This misinterpretation probably occurred due to the ambiguity of the term ‘assurance’ but this has now been resolved.

Finally, past studies revealed that the assurance dimension may have no impact on customer satisfaction or loyalty (Lo et al. 2015; Vryoni et al. 2017). It is possible that they employed a limited number of items in regard to assurance to test their hypotheses. Given the current findings, scholars can now employ a greater number of assurance items to test their hypotheses. Key categories like product, staff and physical assurance may yield interesting or different results, thereby expanding the literature. Similarly, many customers also indicated that certain attributes of assurance (e.g. the skills of therapist, the hygiene of equipment, the quality of products, and communication) can impact their decision making in regard to patronising a spa establishment as well as their satisfaction and behavioural intentions. This suggests the importance of assurance in influencing key variables like customer satisfaction or loyalty. Future studies could implement the current findings to verify this assumption.

4.3 Practical implications

As the assurance dimension in the context of spa service quality can be classified into four categories with individual measurement items, spa practitioners can now implement them more appropriately to better understand customer judgements on the assurance dimension. The findings can help spa managers to improve the management of service quality more appropriately, particularly in regard to the assurance dimension. Without these findings, spa managers may have limited ways to understand customer judgments in regard to the assurance dimension, and may lack the opportunity to deliver superior services. Now, based on the current findings, spa managers can learn how to obtain more information from customers in order to enhance customer trust on spa services. According to the literature (Liu-Lastres et al. 2019; Peco-Torres et al. 2021), service providers need to know that for consumers to resume their consumption, they need to perceive a smaller health risk during service delivery. Implementing appropriate practices during COVID-19 may help customers to avoid feelings of health risk during service delivery, and can enjoy a positive personal experience delivered by professional service staff (Peco-Torres et al. 2021). The more spa managers can implement a wide range of assurance attributes, the better they can provide the services to enhance customer trust and confidence, thus helping to better satisfy customers. The assurance items shown in Tables 3 & 4 can be employed to devise several measurement items to assess customer expectations and perceptions on spa service quality. For example, physical and process assurance may be fully implemented to assure customers about the lower health risk.

In addition, certain elements of assurance may be important in different types of spa. For example, product assurance may be an important element for a five-star hotel or a luxury spa. Spa manager can better understand customer expectations and perceptions on their in-house and retail products. In contrast, other day spas can obtain more information about customer judgements on different attributes of assurance in order to enhance their competitiveness and service quality such as staff assurance, physical assurance, and process assurance. These attributes could have impacts on customer satisfaction and loyalty (Lo et al. 2015; Sangpikul 2019; Vryoni et al. 2017). Importantly, during COVID-19, process assurance, in terms of the measures or practices to prevent the spread of COVID-19, seems to be important for all types of spa, and should be carefully managed to enhance customer trust and confidence in using spa services.

4.4 Study limitations

Some limitations need to be mentioned. The current study examined customer reviews based on spa establishments in Bangkok. Thus the findings may be limited in their relevance to spas in Bangkok, as opposed to other locations. Future studies could investigate other locations to cross-validate the findings of this study. Furthermore, the number of participants, particularly spa managers, was small due to the current COVID-19 pandemic and thus further studies could involve larger samples. In addition, the current study is an exploratory qualitative study with conceptual findings. Quantitative/statistical methods are required to validate the qualitative results obtained from this study.