This research aims to explore the mother tongue of Yunnan Chinese at Mae Salong Nok Subdistrict, in Chiang Rai, and to study the mechanisms of language development of overseas Chinese to use the information as a guideline for planning the language and education policies for the Thai government, and to continue to preserve the mother tongue of the Yunnan Chinese in the future. The population used was 112 Yunnan Chinese. Applying linguistic theories was used, and the data were collected from questionnaires, observations, and formal and informal interviews. The results showed that families, communities, and schools of the Chinese on Doi Mae Salong Nok used their mother tongue as the main language, and their utilitarian identity and sentimental identity towards the Chinese language were very high. This is mainly due to the high clustering rate and intermarriage between ethnic groups, and the acceptance of ethnic identity was excellent.