This study investigates the economics of clean energy transmission infrastructure in Southeast Asia, delineating an advanced integrative model tailored for generation and transmission planning that encapsulates the variable nature of renewable energy sources. It simulates hourly operational dynamics of cross-border interconnections among Southeast Asia, China, and South Asia. The authors analysis took place together with an evaluation of transmission corridors’ economic aspects, including clean energy penetration, degrees of interconnection, and tariffs. Findings elucidate the impact of diverse parameters on transmission corridor’ economic feasibility. The study concludes with recommendations for Southeast Asian pan-regional power grid infrastructure development strategy enhancement.