This analytical note benchmarks where ASEAN+3 economies stand on the emissions–development relationship and discusses implications for medium-term growth. Econometric estimates using a Stochastic Impacts by Regression on Population, Affluence, and Technology (STIRPAT) framework suggest emissions are most strongly associated with income, population scale, and energy use, while Environmental Kuznets Curve (EKC) based turning points should be interpreted as comparative benchmarks rather than country-specific thresholds. To synthesize cross-economy exposure and transition pressure, the note introduces a Composite Environment–Development Risk Index spanning emissions scale, emissions growth, EKC positioning, energy use per capita, and renewables shares. The results point to uneven vulnerabilities across the region.