This book intends to offer an alternative lens for regionalism studies in Southeast Asia. Despite of its widely acknowledged status as one of the most successful regionalism, ASEAN still suffers from numerous obstacles. Yet, in the midst of ASEAN uncertain future trajectories, there is only limited consensus on how to approach ASEAN regionalism. Scholars of ASEAN regionalism tend to use ASEAN identity as the main explanation of cooperation among ASEAN member states. However, this approach suffers from limitations. Emphasis on static, traditional, and all-encompassing identity has made issue-specific cooperation and its internal dynamics neglected. The way issue-specific cooperation alters ASEAN architectures also remains understudied. By shifting attentions to issue-specific cooperation, this book attempts to fully grasp the dynamics of 50 years of ASEAN cooperation. Why could ASEAN member states reach consensus in certain issues—ranging from energy, environment, human rights, disaster management, human security, to infectious disease—albeit ASEAN values such as non-interference and informality? How do these practices of cooperation reshape the idea of ASEAN values? Will the changing practice of issue-specific cooperation spillover to the strengthening of ASEAN regionalism?