I had a job done recently by an Electrical guy, he drove 20km to me, spent 3 hrs sorting out a problem, 45minutes of that in the roof space with 36 deg heat so lord knows what it was like up in that space. When it was all finished, the electrical issiue fixed , he asked for 400 baht ! I gave him double !
I wouldnt have even come out that distance for 400 let alone what he did altogether. So yeah, that boy got a good tip ! Amazing service and VALUE in my book.
Imagine what the cost wouldve been in the West.
Generally out and about, no I dont tip unless its not bothering with "shrapnel" with change, and I dont regard that as a tip, more a convenience for me as I hate coins.