The 10th Semi-Annual Meeting of the Greater Mekong Subregion (GMS) Working Group on Environment (WGE-SAM10) was held on 11 November 2015 in Chiang Mai, Thailand. The meeting was chaired by Dr. Rungnapar Pattanavibool, Director, Office of International Cooperation on Natural Resources and Environment, Ministry of Natural Resources and Environment, Thailand; and co-chaired by Mr. Pavit Ramachandran, Senior Environment Specialist, Asian Development Bank (ADB) and Project Officer for the Core Environment Program (CEP). The meeting was attended by representatives from the environment and other relevant ministries of Cambodia, the People’s Republic of China (PRC), the Lao People’s Democratic Republic (Lao PDR), Myanmar, Thailand, and Viet Nam; the GMS National Secretariats; co-financing partner; ADB and GMS Environment Operations Center (EOC) staff.