Most fights start for a reason in Thailand, unlike in Europe where groups picks on strangers.
Walk away and don't be a stubborn smart-arse and you are pretty 'safe'.
I have actually had more problems with drunk Brits than with Thais so here you are 🙂
Well done. Had a friend 35 years ago who died from Rabies because he ignored our advice to go and see a doctor. Terrible death.
You can try to get a refund from the owner of the dog, but probably hard to prove.
3K+ baht is a small amount to pay so you can sleep at nights without worry.