The Association of Southeast Asian Nations (ASEAN) is at a turning point to drive an energy transition toward a low-carbon future. Investigating ASEAN’s decarbonization strategies is timely. We present a capacity expansion model with hourly resolution for ASEAN to meet net-zero emissions by 2050, integrating electricity generation and hydrogen production. The results show two “bookend” pathways. ASEAN can decarbonize its power sector through an accelerated expansion in renewables and battery storage (up to 95% and battery charge up to 28% in 2050) or an expansion in carbon capture and storage (CCS) and hydrogen (up to 46 and 15%, respectively). CCS is found to play a key role in hydrogen production. For power system operation, grid connectivity can lower battery storage demand and power reserves but requires higher power system flexibility. Our findings can help decision-makers identify the roles of key decarbonization strategies in ASEAN and navigate between various scenarios.