Those who called me a coward will be vindicated by this post. I thought what I would have done in the white guy's situation:
1. Don't drive. I've already "not driven" for 11 years here. But, I live in Pattaya and take a lot of girls, so that is another threat vector (girl gets mad, calls some aggressive guy over, or a bouncer at a club instigates etc).
2. Don't let them stand behind you. He just kept standing there talking to his thai lady, saying things like "why does he keep punching me?" "He needs to stop!"
In that situation I think the best course of action is to give a shocked look and then move away to across to the other side of the crowd, facing his direction but not looking at him.
Now he has to actively keep following you even after seeing your stunned look. In the "thai mob" videos I've seen online the Thais seem to see shock and desperation of the person they are group attacking as the sign that it's enough, "they've won." So maybe this does it.
3. If the aggressor does follow, now you have permission to run. No one including in Thailand has the right to keep pursuing you to punch you in the back of the head every 30 seconds.
There is a legal issue of hit and run but if you call the police (which is what he was doing on his phone) and explain the situation, they should understand.