Regionalism has become a major trend in economic development in Southeast Asia since the end of the Cold War. In the Lower Mekong Basin, riparian states use water for hydropower, which is one of the important potentials of the river. This strategy supports the regionalization of economic activities that is promoted by policies of regionalism, which is aiming for more participation of the private sector and the creation of an integrated regional market. However, large-scale hydropower projects, especially on the transboundary watercourse of the Mekong mainstream, potentially have critical impacts – something that draws attention to the existing arrangements for transboundary water governance (TWG). The disserta