No - most Asian nations did not recognize the South Vietnam govt propped up by Western powers. India for example supported Vietnamese independence from the French and recognized the PRG - Provisional Revolutionary Government which was the resistance movement in South Vietnam.
At any rate, even the US vetoed Vietnamese membership to the UN in 1975 - after losing the War.
I would not say "most". Thailand, Laos, SK, Philippines, Singapore did.
>US vetoed Vietnamese membership to the UN in 1975 - after losing the War.
Because the war was still ongoing, between North and South at that time. They merged in 1976 and US voted in favor of membership in 1977.
Only because Jimmy Carter got elected in 1976 on the basis of a campaign pledge to forgive all draft evaders and beat Ford. Until he was elected, Vietnam was three times blocked from admission by United States vetoes in the Security Council.