This is a study of changed socio-cultural conditions of Thai Mon community at Mae Klong Watershed, Ratchaburi province. The writer endevour to grasp the socio-cultural changes of the Mon community in the aspects related to family institution, educational institution and public health institution. Many beliefs have been gradually changed including causes of socio-cultural changes by physical environmental factors and information technology. However, the Mon still adheres to and practices the traditional socio-cultural tradition and custom.