Doesn't surprise me, so many weird foreigners here, I'd say he's upset the wrong person.
We'll read in the coming days but Probably road rage, I reckon the foreigner has blasted his horn or given the Bird to the wrong Thai guy, the Thai has taught him a lesson and taken his bike.
I see so many foreigners being rude and disrespectful on the roads, they come to Thailand and bring their western childlike road manners with them, never giving way at intersections always yelling and screaming, blasting their bloody horns.
I've got a neighbor, elderly English guy.
He's asked me for help a few times, he asks me to go with him on small trips in his car to pick up different items, he has poor navigation skills.
I had to stop helping him, he's always blasting his car horn for the silliest things, bloody annoying.