Strangely, ist indeed the case that in TH-but certainly not as a general rule, 4/5* HTLs tend to be more restrictive re visitors, whereas the cheaper ones hardly ever do.
Some chains are more notorious for that as others.
The trick in general is to book a DOUBLE room, do not expect to pay for a single and use it as double!
Mostly for BKK: many gay places also can offer for a small surcharge the rent of a room on the spot-these tend to be much much less as 5* however. there are also plenty of ''short time '' HTLs-mostly with curtained off parking spots in front. try it once just for the experience. If you hire a guy he will know such places