Hotels won't care about you bringing a girl home. Covid or no, their policies will be the same "none of our business" that they've always had. Many of them will ask for the girl's ID and will hold it so they can make sure you're alright and everything is fine before they let her go. Others will just waver her in and out. Depends how upmarket the place is, but that won't have changed.
You won't be in at 11pm and out any time soon this time. Assuming you're coming under some sort of test and go you'll be pretty much confined to your hotel until at least the first day.
I'd imagine Bangkok and Phuket will be about the same in this regard. The big difference is that gogo-style bars in Phuket are open, and they're technically not in Bangkok.