2nd, Cambodia wasn't traditional part of Vietname. It had its own Khmer Empire. Then Thai or Siamese took over the empire. "Vietnam's settlement of the Mekong Delta led to its annexation of that area at the end of the seventeenth century ... Such foreign encroachments continued through the first half of the nineteenth century because Vietnam was determined to absorb Khmer land and to force the inhabitants to accept Vietnamese culture" (from Wiki). So Vietnam, in history, didn't have complete control of Cambodia at all, only small parts. This disproved your talking about 柬埔寨在历史上属于越南版图 nonsense. 1863, it went under French control. But King Norodom Sihanouk, in 1953, had negotiated independence of Cambodia from French control. "Neutrality was the central element of Cambodian foreign policy during the 1950s and 1960s. By the mid-1960s, parts of Cambodia's eastern provinces were serving as bases for North Vietnamese Army and Viet Cong (NVA/VC) forces operating against South Vietnam, and the port of Sihanoukville was being used to supply them ... In March 1970, while Prince Sihanouk was absent, Prime Minister Lon Nol deposed Prince Sihanouk and assumed power through a vote of the National Assembly. Son Ngoc Thanh announced his support for the new government. On October 9, the Cambodian monarchy was abolished, and the country was renamed the Khmer Republic. Hanoi rejected the new republic's request for the withdrawal of NVA troops. 2,000-4,000 Cambodians who had gone to North Vietnam in 1954 reentered Cambodia, backed by North Vietnamese soldiers. In response, the United States moved to provide material assistance to the new government's armed forces, which were engaged against both the CPK insurgents and NVA forces." So now Vietnam begun boldly taking Cambodia lands.
越南侨民企图建立亲越柬埔寨政权? "The Communist insurgency inside Cambodia continued to grow, with supplies and military support provided by North Vietnam. Pol Pot and Ieng Sary asserted their dominance over the Vietnamese-trained communists, many of whom were purged. At the same time, the Communist Party of Kampuchea forces became stronger and more independent of their Vietnamese patrons." Are u refering to this? Were they even legal under laws of the Khmer Republic? Both Pol Pot and these 越南侨民 are communists INSURGENTS to the Khmer Republic. They were not legalized in anyway at the time nor in any political position within Khmer Republic (Cambodia). It was only after Pol Pot took control and its Democratic Kampuchea begun to have problems with Vietnam, did PRC established a good relation with Cambodia to counteract Vietnam-USSR rivalry.
You just like to confuse people and make slandering statements without checking them, do you? Feel very sad for you.