unfortunately there's really no Persian sources in existence on vietnam, at most there's tourist websites covering Phu Quoc Island, Hanoi, Saigon... I am doing a systematic and consistent transliteration into Persian (including some judgements to match Vietnamese phonology. For example "An Giang". Since Vietnamese is derived from Portuguese/Western-Europe, the second syllable, it's pronounced not as гянг, but as джанг (if you can read Cyrillic). so I've transliterated accordingly. Generally i simplified complex sounds that don't extent in Persian, following what's done on Persian Wikipedia. For example whenever there's the "nh" anywhere, I simply wrote as "n", or "th" as "t".