Yeah, Cambodia is a weird case. The Khmer Rouge developed a weird anti-Vietnamese ethno nationalism, and then when the Vietnamese kicked them out of power, they installed an actually Socialist government, The People's Republic of Kampuchea, but it was ultimately unable to survive the collapse of the Comecon, the Socialist trade bloc, and the continual Khmer Rouge insurgency.

The UN had to step in at one point to administer things, and it ultimately ended in the re-establishment of the Cambodian monarchy