You do know that Pol Pot (then called Saloth Sar) came into contact with communism in Paris via the French Communist Party (PCF)? He was attracted to communism because of the PCF's anti-colonial stance, which caused them to be pro-Vietnamese independence, also implying independence for Cambodia (both under French rule). Sar, upon returning to Cambodia, actually joined the Khmer People's Revolutionary Party, basically a Viet Minh controlled front. This is the origin of the Khmer Rouge.
Now, China did support them once the KR was up and running, because of their anti-Vietnamese stance stemming from centuries of animosity between Cambodia and Vietnam (with the latter taking the Mekong Delta from the former in the 18th century). The US was more than happy to support them as well, due to that same anti-Vietnamese stance, even after they were driven out of power and into the jungles in the 1980s.
first Cambodian fall under the French then the Chines Now and the final stage Vietnam.. wake up Khmer people look at our history 20 years from now we won't be able to have a country....