International tourism is an important part of international trade in services. It involves a large number of industries, and wealth transfer between countries. Then, the paper analyzes the current situation of the tourism trade in Thailand in recent ten years uses the comparative advantage index to analyze the competitiveness of international tourism services of Thailand. Then an empirical analysis of the relationship is made between the economic development and the income of tourism service trade. The paper gets conclusion that Thailand's tourism trade could provide jobs, promote full employment, and successfully improve the level of economic development in Thailand.