Knowledge Sharing on Environmentally Sustainable Cities Management Regarding Thailands Philosophy of Sufficiency Economy was held on 26-29 August 2015 in Petchaburi-Prachuap Khiri Khan-Samut Songkram Province, Thailand, organised by Office of Natural Resources and Environmental Policy and Planning (ONEP), one of Thailand?s Ministry of Natural Resources and Environment departments. The Workshop is one of the activities to contribute to one of ASCC goals, to ensure that cities/urban areas in ASEAN are environmentally sustainable, while meeting the social and economic needs of the people, as noted by the 13th Meeting of ASEAN Working Group on Environmentally Sustainable Cities (AWGESC) held on 6-9 July 2015. Its objective is to share experiences in academics and technology for the sustainable management of urban environments under Thailands philosophy of sufficiency economy. The Workshop is the first knowledge sharing activity of Environmentally Sustainable Cities management using the concept of Sufficiency Economy implemented as best practices. The Workshop provided participants the opportunity to visit The Royally Initiative Projects including The Sirindhorn International Environmental Park (SIEP), Laem Phak Bia Environmental Research and Developmental Project (LERD), Royal Biodiesel demonstrative project, and Amphawa Chaipattananurak Conservative Project. The Workshop was attended by delegates from Cambodia, Lao PDR, Malaysia, Philippines, Vietnam and the ASEAN Secretariat. Office of Natural Resources and Environmental Policy and Planning (ONEP) was the organizer in cooperation with Khon Kaen University who provided resource persons. The opening remarks was delivered by Mr. Somsak Bundao, Director of Urban Environment and Area Planning Bureau, ONEP. A video presentation which followed the remarks highlighted the Sirindhorn International Environmental Park (SIEP) establishment to serve as a living natural museum and to expand and disseminate the works on the conservation of energy, natural resources, and environmental in light of the initiatives of the King. One of the SIEP area observed is mangrove forest which is a restoration of the coastal mangrove ecosystem to a sustainable state. Dr. Sonjai Havanond from Khon Kaen University who presented Adaptive Mangrove Management in Thailand A climate change adaptation: Case study for Sirindhorn International Environmental Park showed that the restoration of mangroves will reduce coastal erosion, provide more breeding sites for marine species and aid the regeneration of fish stocks. The observation continued on the second day which was visiting The King?s Royally Initiated Laem Phak Bia Environmental Research and Developmental Project. There were five technologies developed to solve the environmental problem of solid waste and wastewater. They are based on the principle of self-purification process or utilization of natural means to habilitate deteriorated natural resources. The technologies include oxidation pond, grass filtration, constructed wetland, mangrove forest filtration, and concrete box, which are all simple and easy to practice. The next project visited was Chaipattana Foundations Key project for renewable energy-vegetable oil refining and Bio-Diesel integrated production plant in Hua Hin District, Prachuap Khirikhan Province. The foundation was first assigned by Princess Maha Chakri Sirindhorn to carry out experimental study on oil palm for alternative energy. The development of began in 2006 and now the plant serves as a model for environmentally-friendly bio-diesel production. The last day activity was visiting Amphawa Chaipattananurak Conservation project located in Samut Songkram province. This is one of Chaipattana Foundation projects with main aim is to have all the people of Amphawa join in the project by preserving and reviving the customs of the Amphawa community. The local product shops, agricultural demonstration garden, and the community market ground are among those featured in this conservation project. They ascribe to development around the local way of life so that people have jobs and are able to earn their living as well as preserve the environment and local lifestyle. In this way, the community can remain strong, uncomplicated, sustainable, and happy amidst rapid social change. In the final part of the workshop, sharing and discussion was held to get all participants ideas and comments about the observed sufficiency-economy-based project implementations.