There used to be many Chinese living in Vietnam, especially Saigon and other regions of South Vietnam. Before the North occupied Saigon, there were 11 districts in Saigon, 5 of them were mostly Chinese.

Chinese were hardworking and financially successful. Because they were rich, they became the target of the Communist regime, similar to how rich people were murdered in Mainland China after 1949. Fearing the persecution by the Communists (Viet Cong), the Chinese had to leave their homes in Vietnam. Many of them went to North America as refugees.

I believe that some others went back to China since there were many 越南华侨农场 in Canton Province.