This research surveyed and investigated Karen ethnic communities in Suphan Buri, Uthai Thani and Nakhon Sawan provinces from November 2018 to August 2019. The descriptive anthropological methodology was utilized by means of in-depth interviews and participatory observations in important rituals. It is reflected that dynamics of Karen communities in Suphan Buri and Uthai Thani provinces had changed under the impacts of development in terms of forest and land use. Legal issuance about forest and land has affected the rights and ownership of natural resources as well as community origin. The change in the method of production change was from the crop rotation practice to more single crop cultivation. Furthermore, cultural changes were different from community to community under various religious cults, e.g., the beliefs in yellow threads, white threads and drinking boiled water. Those in Suphan Buri and Uthai Thani provinces have had the Chao Wat cult as their belief and cultural center. They also have been forced to adapt to tourism and community development in the Huay Kha Khaeng buffer zone. For those in Nakhon Sawan province, they are not indigenous communities but are migrants from Myanmar coming to work in the province and are a group formation from transnational laborers to organize cultural activities. The ceremony of knot-tying on the wrists is an important cultural and political activities of transnational Karen workers.