This study explores the impact of ChatGPT on STEM pedagogy in Higher Education Institutions (HEIs) across the ASEAN region, focusing on its effectiveness, challenges, and the pedagogical shifts it may inspire. Using a mixed-methods approach, the research surveyed 300 educators and 1,000 students, supplemented by interviews and focus group discussions. The findings reveal that ChatGPT significantly enhances student engagement and understanding of complex STEM concepts, aligning with constructivist learning principles. However, challenges such as technological barriers, concerns about content accuracy, and the need for professional development were also identified. The study concludes that while ChatGPT has the potential to transform STEM education, its successful integration requires addressing these challenges and ensuring the tool is adapted to the diverse cultural and educational contexts within ASEAN. Recommendations for practice and policy include investing in infrastructure, providing tailored professional development, and developing culturally responsive AI tools. This research contributes to the growing literature on AI in education, offering insights for future research and practical implementation.