I live here for 2-3 weeks every month. I would say depends on venue and yourself.
Streetfood stall , NO NEVER
Restaurant where you are serve like a king, have someone pour your drinks for you, switch out your waste plate ( they give u a small plate where you dump your prawn/crab shells/ fish bone) when you are having seafood with shells, YES.
Taxi or driver, YES. It is not fun driving in Bangkok or Thailand in general.
Parking attendant, YES but only on land where the restaurant own the parking lot, you dont pay the parking fee but you pay the attendant instead, they do really take care of your car. If they dont own that land a receipt will be issued.
Premises that involve alcoholic drinks or premises with pretty women/dude services, YES
Massage, YES
Apart from alcoholic and pretty women/dude places, this people earn little wage and living cost in Thailand is getting damn high, especially in the capital.
The amount depends, typically 20 to 50. 100 baht is too much unless the particular person go all out to serve you, or party venue.
Before leaving, a word of chok dee is also nice.
Not paying tips is ok.
I would say one thing for tips, it is not necessary and depends on yourself entirely. If you're feeling generous and think the service deserves more, you are more than welcome to tip.
Got it, thanks for the detailed info. Appreciate it