The thesis investigates the maintenance of ethnic identity by the Mons in three villages of Ban Pong District, Ratchaburi Province, by taking into consideration their expressions of ethnic identity and learning as well as their ethnic boundary and rituals. The author views the relationship between ethnic maintenance and rituals based on the Theory of Ethnic Maintenance and the Theory of Ritual Analysis, consisting of three main factors, namely group, history and identity. It is found that there are two levels of ethnic identity in the Mons, the level of being Thais and the level of being Mons. The Mons are a part of Thai society but they express their ethnic identity via their traditional dress, language, animistic rituals, and merit-making ceremonies during Buddhist holy days.