If you are a young lady (20-30) in southern Vietnam, how do you decide between saying anh or ong (for a close friend who is older than you) ?
1: If his age is more than ___?
2: How does your own age (help you decide) when you choose anh or ong?
3: How would your choice (of anh or ong) be changed by affection or respect?
(edited to be more clear about what I am asking)