Transboundary air pollution remains a major regional challenge in Southeast Asia because Malaysia, Thailand and Cambodia use heterogeneous emission classifications, data formats, spatial resolutions and estimation practices. This project will develop a harmonised, high-resolution emission inventory framework tailored to Southeast Asian conditions. An adapted and tropicalised TEDS-based approach will be aligned with IPCC inventory principles and integrated with GIS, satellite observations (TROPOMI, MODIS, Sentinel), available ground observations and AI-assisted data fusion. Common classifications for point, area, line, biogenic and open-burning sources will enable comparable estimates of PM2.5, SO2, NOx, CO and NMVOCs at 1–5 km resolution. A tiered validation and uncertainty framework will address heterogeneous data availability, particularly in data-sparse areas. Early stakeholder co-design will define priority sectors, data needs, validation requirements and policy applications. Outputs will include harmonised national datasets, a regional emission database prototype, scientific publications, technical and policy briefs, and training. The project will strengthen regional research collaboration, early-career capacity and science–policy interaction, supporting SDGs 3, 11 and 13 and evidence-based transboundary air-quality management.