Actually.....its hard to find a hotel in Bangkok that is not guest friendly
especially in the areas where actions are near. The only ones that is probably out of bounds are AirBnBs most of the time especially those who put a CCTV at the front entrance and warn you that they do check on the recordings to see whether you bring in more than who you originally checked in. But for hotels in the action areas, its just a matter of how strict the hotel wants to be in terms of enforcing that the girl leaves her ID behind or whether a 3rd person needs joiner fee etc....