This paper investigated the current status of hydropower development of ASEAN members and established the hydropower digital planning model, which includes the method for the extraction of the digital drainage network, banded contour line, and stage-storage relation curve based on the secondary development of ESRI ArcGIS 10.2. Then, the theoretical capacity and the hydropower development potential of the main drainages in ASEAN-8 were analyzed based on the proposed hydropower digital planning model. Furthermore, the relative potential electricity markets for the untapped potential sites were analyzed, and the perspective long-term plan for the interregional interconnection among ASEAN-8 members was proposed. Finally, the incentive policies toward foreign investors in ASEAN-8 and the investment environment for China's hydropower enterprises were analyzed. This study shows that Indonesia, Laos, and Myanmar have the richest untapped hydropower resources with the exploitable installed capacity of 61 191 MW, 21 612 MW, and 55 687 MW, respectively. It is found that there is enough electricity market for the untapped hydropower potential sites if the international power exchange could be achieved successfully. This study also indicates that Indonesia, Laos, Malaysia, and Myanmar have a more favorable hydropower investment environment for China's hydropower enterprises.