We don't have synonyms for Vietcong yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are viet cong and netcong.
(n) :
A communist organization and guerrilla army in South Vietnam and Cambodia that fought the United States, South Korea, Australia, and the South Vietnamese government during the Vietnam War and was supported by communist North Vietnam.
(n) :
A communist organization and guerrilla army in South Vietnam and Cambodia that fought the United States, South Korea, Australia, and the South Vietnamese government during the Vietnam War and was supported by communist North Vietnam.