Microplastics exhibit a global distribution and have been detected at all levels in the aquatic environment. It is estimated that 15-51 trillion microplastic particles have accumulated in the ocean, weighing between 93 and 236 thousand metric tonnes. The microplastics pose a great threat to the entire ecosystem by entering into the food chain through aquatic organisms. Toxicity of the pollutants is caused by the plastic polymer itself, or by other chemicals that adsorbed. Microplastics are detected in freshwaters of Europe, North America and Asia. However, there is a lack of knowledge about the status of these pollutants in Southeast Asian countries. Thailand, Vietnam and Indonesia are selected as the study sites. All three are facing a serious problem in management of water bodies such as rivers, estuaries and sediments. This project will help to explore the current situation of microplastics pollution including both quantitative and qualitative characteristics in Chao Phraya River (Thailand), Saigon River (Vietnam) and Citarum River (Indonesia). The appropriate management strategies for the microplastics will be proposed.