<p>Driven by the growing awareness of environmental issues, particularly air pollution, the adoption of electric vehicles (EVs) is spreading globally. This includes Southeast Asia (SEA), where Indonesia, Thailand, and Malaysia have set ambitious targets for EV adoption along with domestic EV manufacturing. On several occasions, these three countries appear to compete for investments from automotive companies and key EV component manufacturers. This study aims to assess the competitiveness of EV manufacturing in Indonesia, Thailand, and Malaysia. This study employs the Porter Diamond Model as the theoretical framework, combining secondary data and expert assessments to score each country across multiple indicators. Relevant secondary sources such as government reports, regulations, and prior studies were collected, while surveys and semi-structured interviews were conducted with experts from the three countries as well as non-SEA experts, to ensure objectivity. The secondary data were quantified using a 1–6 scale, and expert evaluations were aggregated into final scores for each indicator by country. The findings reveal that each country possesses distinct strengths that can be leveraged to achieve competitive advantages. Thailand has strong policies that support the development of the domestic automotive ecosystem; Malaysia excels in charging infrastructure and industry localization; and Indonesia has key natural resources essential for EVs. The final assessment shows that Thailand emerges as the leader, followed by Malaysia and Indonesia with equal scores. This study is the first to compare EV manufacturing competitiveness across the three countries and contributes to EV adoption, manufacturing, and ecosystem growth in SEA.</p>