Every language has its longstanding conventions. Vietnam and Korea have a shared linguistic heritage as part of the Sinosphere. Transcriptions between the CJKV orthographies are normal, expected, and standardized – not an ad hoc guess by someone sitting in an armchair halfway around the world. I have no idea what the usual practice is among Persian speakers, but Korean is totally irrelevant, and by bringing it up you’re casting doubt on whether you know what you’re doing.