There are those who seek to justify their stinginess by telling us it’s not part of Thai culture to tip. I’ve asked many Thai friends their opinions on tipping and it’s always had the same response. Tip but tip appropriately, which is exactly what I’ve always done. I’ve had a few people decline a tip but it’s never been on the grounds of finding it insulting. There’s no harm in tipping someone who may well be in a low paid job, your tip could buy their lunch and your small gesture helps improve their life.
My battery failed once at a petrol station and a taxi guy offered to get me going, he spent about 20 minutes with me and point blank refused 100 baht from me.