The book investigates cultural changes of the ethnic Phuan in the Central Plains of Thailand. The objective of the study was to politically survey the Phuan’s population movements, settlements, and their adjustment to the Thai socio-economic conditions. The author collected textual data to obtain an historical overview of the ethnic group and field data at Ban Mee District. Lop Buri Province, to understand their current socio-cultural conditions. The assimilation concept was used to explain their cultural changes. It is concluded from the study that changes from a subsistence economy to a money-oriented economy obligated the ethnic group to adjust their livelihood from subsistent rice cultivation to commercial rice cultivation. The focus was more on productivity rather than sufficiency and rice cultivation-related debts accumulated. Many turned to better paid jobs than rice cultivation. However, the changes enabled them to pay more interest in maintaining and preserving their ethnic culture.