When the Vietnamese expansionists swallowed up the Kingdom of Champa, they forced the Cham people to adopt the Vietnamese last name of Nguyen and changed the Cham royal last name of Po to Pham, etc. For example, Vietnamese leaders Nguyen Van Thieu and Pham Van Dong were of the Cham lineage.
The tradition continued with the expansionist Gia Long r. 1813. Due to the repeated invasions by Thai forces and the endless internal royal succession conflicts, the Vietnamese opportunists were able to exploit the Khmer weaknesses and detached a huge tract of southern part (Kampuchea Krom) of Cambodia for themselves. According to the books by Vietnamese authors Le Huong and Nguyen Dinh Dau, the Vietnamese royal chronicles listed the following assigned Vietnamese-sounding last names for the Khmer Krom people who only went by just their first names.
List of Khmer Krom's assigned Vietnamese-sounding Last Names:
However, the Vietnamese author Le Huong of the book "NguoiVietGocMien" noted that the Khmer Krom people from certain provinces tend to adopt only particular Vietnamese-sounding last names. For example, Krom Krom from the provinces Preah Trapeang (Tra Vinh) and Long Hor (Vinh Long) adopted the last names of Thach, Kim, Son, and Kien. The Khmer Krom from the province of Preak Reussey (Can Tho) adopted the last name Dao. The Khmer Krom from the province of Kraw Mourn Sor (Kien Giang), the men adopted the last name Danh, while the women adopted the last name Thi. The Khmer Krom from the provinces of Khleang (Soc Trang), Pul Leu (Bac Lieuu) and Tirk Kmao (Ca Mau) adopted the following last names: Ly, Lam, Tran, Trieu, Luu, Huu, Hong, Dung, Tang, Cau, Tram, To, Truong, and Huynh
Notable Khmer Krom last names identified and monitored by the Vietnamese government include Thach, Son, Tran, Lam, Kim, Danh, Chau...
Khmer Krom people share the same bloodline of the Khmer people who built the famed Angkor Wat and the various temples that dot the Khmer Empire. When the Thai invaders challenged the Khmer ownership of the Khmer temple of Preah Vihear, educated Khmer Krom intellectuals by the last names of Son and Truong went to defend the Khmer honors and temple against the Thai invaders and won back the temple in the international court for Cambodia.
So Cambodians must learn to differentiate between who are the ethnic Khmer Krom and who are the ethnic Viets. Just because our long lost relatives have a new sounding foreign last names, it does not mean that they are UNKHMER.