Violent conflict is the most visible threat to the achievement of sustainable development in any society. The source of conflict is conventionally the warfare among countries. In the last fifty years, however, the cause for conflict has changed and been mostly related to the process of nation building in the post-colonial states in Asia, Africa and Latin America. In the new nations, conflicts on the choice of state's ideology are perhaps the most common, and if unresolved, often lead to the separation or partition of the respected nations. In this case, China vs. Taiwan and India vs. Pakistan are perhaps good examples in history. While ideology plays a critical role, it cannot be isolated from the influence of seemingly non political factors of demography and ethnicity. Majority-minority group conflicts are always related to the demographic composition of the population in which ethnicity, religion and economic classes are politically played out. In the aftermath of the Cold War, ethnic conflicts were unleashed. And they often led to the disintegration of nation-states. The breakdown of the Soviet Union, Yugoslavia and perhaps Indonesia are illustrative cases. Myron Weiner, Thomas Homer-Dixon and Milica Zarkovic Bookman are among the pioneers in studying the interconnectedness of demography, politics and conflict. Ethno-demographic composition and its influence in the politics of nation building generally has been overlooked in many theories on violent conflicts. This paper is an attempt to contribute to the discourse on the nexus of population and conflict by assessing the existing theoretical knowledge and its empirical evidence from the Southeast Asian region.