The purpose of this study is to review the changes of the relationship between the civil society and the military, and to understand the dynamic influence of it to political development in Thai politics. According to the strength of civil society and the influence of political or economical crises, the weakness of civil society and large or small crises have induced the political intervention of the military, and the military’s internal factionalism has made a series of military coups from 1932 to 1973 in Thailand. In 1973, the first democratization has occurred, and this was because the civil society has became more stronger. From 1973 to 1976, the military was withdrawn externally from Thai politics. However its strength was not enough to secure Thai democracy, and the expansion of communism in Indochina threatened the Thai security. Therefore, the military coup occurred again in 1976, and Thai politics was controlled by the military-civil society coalition during the 1980s. In 1991, the military coup recurred, but this coup did not have any moral justification or the state of urgent crisis. Consequently the political intervention of the military was confronted with the strong resistance of the civil society, and withdrawn from Thai politics.