Many Khmers continue to view the Vietnamese with resentment and suspicion. And this has been influenced by the tense history between Cambodia and Vietnam. Periods of wars and immigration between the two countries have led to a significant population of ethnic Vietnamese living in Cambodia.
According to a 2014 report, it is estimated that nine in ten Vietnamese in Cambodia are undocumented. The Cambodian government attributes that figure to illegal immigration. This attribution overlooks a significant population of Vietnamese in Cambodia today that can be traced to mass immigration that occurred over a century ago during the French rule over Indochina when different laws governed the country. After the French withdrew from Southeast Asia, targeted discrimination of Vietnamese by the Khmer Rouge attempted to purge the existing ethnic Vietnamese population from Cambodia by deportation and execution. Those not executed had their possessions confiscated, including birth certificates and other documentation that proved their citizenship.
In full: https://www.devdiscourse.com/article/politics/455140-vietnamese-in-cambodia-still-denied-citizenship
