I was last in Hanoi about 5 years ago & the highlight was a visit to the Ami Spa.

Their offering was a 1 hour package, where you have a short sauna, body scrub & about 30 minutes massage, starting in underwear & ending without it.
Their lads were very fit, slim with some muscle & they were energetic.
If I remember correctly, they allocated the masseur & they had over 10 of them, with only 4 rooms.

https://www.google.co.uk/maps/place/...5f63f9e3?hl=en

No idea if it's still open, however considering there is so little on Vietnam posted AND their very good service, I'm posting it.

I also visited 2 saunas and a gay bar, without much success.