There are hotels that are advertised as "gay friendly", but they all seem really expensive, for some reason (at least by SE Asian standards).
I usually just a find a well reviewed joint, that has a price I like, and take my chances that the guy on the counter at night is reasonably chilled. I've been to Saigon at least seven times now, and never had a problem - except once, when the guy insisted that if my off was staying all night, that I pay extra for double occupancy.
My impression is that most hotels in Vietnam don't care if you bring someone back, as long as you're discrete.
Had 6 nights there back in July. Spent most the time just catching up with a couple of friends, as socialising in the straight bars. But I also met 3 different offs via the apps. Seems to be where it's all happening.
My impression has always been that there's no specific gay culture in sgn - that Vietnamese people are so casual about it, that gay people just blend in with the rest of the Nightlife. But I read on the web recently that there a few different speciality gay bars have opened there recently (see Google). Didn't try them. Maybe next time.