How much do you usually tip a masseuse?

So it’s my first time in Bangkok, and I went for a 2 hrs massage. Where I’m from, which is one of the Asian countries as well, doesn’t have a tipping culture so I’m not used to it. So here since the masseuses were very nice, I tipped 20 baht and in hindsight, I believe it was too little. When I handed it to her, she might have said something like isn’t it too little but at the time I wasn’t sure what she was saying. Afterwards her demeanor changed completely. So to avoid next time, how much for the tip is expected here?