School-based mental health interventions are considered to have potential for the promotion of mental health in developing countries. We held a workshop to discuss the promotion of mental health in schools in southeast Asian countries. This review report aimed to summarize the current situation of school mental health in Association of Southeast Asian Nations (ASEAN) countries as reported by their representatives in this workshop. To summarize the current situation of ASEAN countries in relation to school mental health, we qualitatively analyzed the content of the discussions from four perspectives: (i) laws and regulations: (ii) mental health services; (iii) teacher training on mental health; (iv) mental health education for students. With regard to school mental health laws and regulations, this report could not provide clear conclusions because the laws were reported through the personal understanding of the public officers. Our results show that mental health services in schools are centered on professionals such as guidance counselors, although the coverage varied among the different ASEAN countries. Only Singapore conducted mental health training for teachers in a comprehensive way, and the number of people who were actually trained in other countries was very limited. Cambodia, Malaysia, Myanmar, Philippines, Singapore, and Thailand included mental health education for students in health education or life skills subjects.