This dissertation is a qualitative examination of how the anti-dam movements, with so many disadvantages, are able to pursue their goals in a hybrid democratic political system in Thailand. This dissertation tries to prove that the extra-bureaucratic influence, which emerges from the anti-dam movements are gaining their foothold in the dam politics of Thailand and become a major cause in increase in pluralism in the fragmented authoritarian regime of Thailand. There are two major arguments in the dissertation: Firstly, FA framework, which has already been proved applicable to China by Lieberthal and Oksenberg in 1988 and by Metha in 2008 is also applicable to Thailand. Second argument is that the success of anti-dam movement should not be judged simply by the ability to cancel the project. If we only consider the ability to cancel the project, we may either overestimate or underestimate the ability of anti-dam movement. However, it does not mean that the ability to cancel the dam project does not count at all or should be excluded completely because it still proves the short-term success, which means that the project is cancelled as that moment. In sum, the ¡§success¡¨ of the anti-dam movement mentioned in this dissertation is the ability to transform the state¡¦s decision-making process for the dam project into the direction of more pluralism and less of authoritarianism so that individuals and groups both inside and outside the traditional arenas of policymaking have increasing role in the policy process. Thus the ability to cancel the dam project is an additional indicator not the main one. This view is illustrated through the four case studies: Bhumibol Dam, Nam Choan Dam, Pak Mun Dam, and Kaeng Sua Ten Dam.