Accualy , i think, there isn't a tipping practice in Thailand. Ok in the big cities they used now foreigners give tips and maybe expect we give.
But this year we made a round trip Nan-CM-Nan and visited all the cities on the road.
I like to eat in small restaurants where only Thai come to eat. And this year, again, i did have 4-5 very confused waitresses when i gave them a tip. My wife did need to explain them it was a tip.
In hotels me usual leave 100bht/a night with a max of 700. And also in the hotels sometimes they come run after me for bring back the money because they think me forget or call the front desk ask them for them to hold me for give back the money.