Have not visited Hanoi, but have visited HCMC (plus Na Trang and Da Lat).

Be prepared for it to be potentially very VERY hot in HCMC - 5 minute stroll from my A&EM Royal Palace Hotel (recommended) to Ben Thann market left me completely drenched in perspiration.

Only found one gay bar - "Godmother" in the City Centre. They have accomodation rooms above, if you fancy that. The crowd was entirely Vietnamese, no non-asian at all - so you might well be lucky if some Vietnamese boy is curious to try something new! I've never had a massage, so I don't notice such places and therefore cannot comment on their availability or lack of it.

Prostitution is very much looked down on, so is not as readily available as a regular Thailand visitor might expect - and I think you might have some difficulty with bringing "visitors" back to your hotel. In the end I had no difficulty sharing a room with my my bf as he was registered with me, but (over 4 different hotels) I certainly did not see any sign whatsoever of older guys bringing younger ones back (and I do tend to notice that sort of thing!)

Thailand it ain't, but a lovely city (quite European in some ways) ,lovely country, and nice people.

I wrote a fuller trip report on Vietnam around June/July of this year, if you want to seek it out. Anything else, send a PM.