Just find some oriental people and listen to them talk in their native language. I can help you tell them apart.
If it sounds like they're constantly saying HOTDOG BUN, they're vietnamese.
Chinese people sound like they're saying CHINGCHONGCHING,
Japaense people sound like they're angry with you, even if they're not looking at you. They kind of bark.
Phillipinas speak better english than you.
That's all i got. if they don't fit into any of those I don't know.
Oh yeah and since you want a vietnamese wedding, look for a Nguyen wedding. I think they all have a last name of Nguyen.