The dynamic economies of the Association of Southeast Asian Nations (ASEAN) have individually concluded many standalone bilateral investment treaties (BITs) and a growing number of bilateral and regional free trade agreements (FTAs), supplemented by intra-ASEAN and ‘ASEAN+’ agreements. These aim to facilitate and protect burgeoning foreign direct investment (FDI) flows, outlined in Part 2, including large outflows recently from several states. Part 3 outlines treaty-making trends, including considerable consistency from many member states as well as some interesting innovations, against the backdrop of persistent problems of poor governance. Part 4 highlights nonetheless the relative paucity of investor-state dispute settlement (ISDS) claims against ASEAN member states, with only a few adverse awards, which helps explain why treaty-based ISDS has not been abandoned. Part 5 also notes several contributions from this ISDS case law to international investment law, and Southeast Asia’s potential to keep influencing its trajectory.