This study was a survey research in order to study health service utilization in Thailand and selection of country for health service utilization of Japanese visitors in Thailand. Data was obtained from interviews with 2,520 Japanese at the passengers’ international departure terminal, Donmuang International Airport during March-May, 2005. Data analysis was done by means of percentage and Binary Logistic Regression. Dependent variables of health service utilization were health service utilization at hospital and spa/massage utilization in Thailand. Independent variables included gender, age group, education level, occupation, monthly income, purpose of traveling, and illness during a stay in Thailand. Dependent variables of selection of country for health service utilization consisted of selection of health service utilization in Thailand while independent variables were gender, age group, education level, occupation, and monthly income in order to determine factors affecting health service utilization in Thailand and selection of health service utilization in Thailand. Research results showed that, at the statistically significant level of .05, health service utilization at hospitals in Thailand depended on purpose of traveling and illness during a stay in Thailand. This indicated that the sample group that traveled for receiving treatment had more opportunity of using services rather than traveling for business/meeting purpose. The sample group that had illness symptoms was more likely to use services compared to the group that did not have any symptoms of illness. On the other hand, spa/massage utilization in Thailand depended on gender and illness during a stay in Thailand. This showed that females, was more likely to use services compared to males while the sample group with illness symptoms as more likely to have service utilization than those who did not have any symptoms of illness. In terms of selection of health service utilization in Thailand, selection depended on gender, age group, and monthly income, which indicated that females had more opportunity of choosing spa/massage utilization in Thailand compared to males while the sample group with monthly income above 300,000 Yen was more likely to choose spa/massage utilization in Thailand than the group with monthly income below 100,000 Yen. In terms of long-term care, annual health check-ups, and general clinic, it was found that the sample group aged above 30 years old had more opportunity of selecting service utilization in Thailand than the group aged below 29 years. This research recommends that the Government should not become the supporter of health services trade or promote the market by encouraging foreign patients to come and use services in the country. More responsibility should be given to the private sector while the pubic sector should focus its role on quality control and appropriateness in service provision.