This research aims to 1) to study the personal factors of Thai and foreign tourists towards their buying decision making behavior in spa products; 2) to study the current situation of buying decision making behavior for the development spa products entrepreneurs to drive the strategy of Thailand 4.0 and 3) to create behavior patterns of purchasing decisions to develop spa product entrepreneurs driving the strategy of Thailand 4.0. The research used mixed methods qualitative and quantitative. The researcher applied qualitative methods by interviewing 21 selected key informants. The data obtained from qualitative was used to construct the questionnaires which were used to gather quantitative data and analyzed by multiple classifications. The researcher determined the sample size to represent the population using the G*Power program. The research tools used in this research were 1) an in-depth interview and closed-ended questionnaires for qualitative research and 2) a questionnaire obtained from the qualitative research using the Delphi technique as a reviewed questionnaire for quantitative research. The questionnaires were distributed to the 305 samples. The results of the hypothesis testing of personal data were as follows: gender nationality age education level source of information that brought them to Phra Nakhon Si Ayutthaya Province and participants traveling to Phra Nakhon Si Ayutthaya Province are the factors that affect buying decision making behavior spa product of model buying decision making behavior for the development spa products entrepreneurs to drive the strategy of Thailand 4.0 strategy. The result of hypothesis testing factors affect the buying decision making behavior for spa products come into 6 factors are local identity product usage buy as a souvenir repeated buying information from reliable sources and the interpersonal factor of entrepreneurs or salespeople. All of these results comply with the assumptions.