This thesis compares Thailand',s relations with the United States and China from 196541975, The realist as-sumes that the structure of power in the internationall system determines overall relations between states' First, this study describes the power situation in southeast Asia in 1965, The next steps are concerned with the study of Thai-U, S. relations and Thai-Chinese relations, The thesis finds that Thailand's relations with the United States and China are determined by the structure of power. When a major power like the United States changes its policies to accommodate China, Thailand, which is a small country, turns to be more friendly with China, These attitudes correlate with the realist assumption,.