The second Trump administration has reversed US climate policy, withdrawing from the Paris Agreement and defunding key international climate initiatives. This move creates a leadership and resource vacuum that weakens global climate action and leaves vulnerable regions like Southeast Asia facing direct financial and technical setbacks. Furthermore, the administration’s policies accelerate climate-health damages by prioritising economic and military goals. The disruption arising from these changes, however, creates an opportunity for ASEAN to assert regional leadership. This report recommends a three-pronged strategy involving (1) establishing leadership in global carbon markets by harmonising a regional framework, (2) championing multilateral climate diplomacy with key partners, and (3) pioneering a regional data and resilience hub to counter the loss of US scientific support.