It is news to me, first time I read the story. And I had to check again to get the facts, yes it was actually a road rage.
I have had some encounters with aggressive Thai males on the road myself , and once inside a shopping mall, I learned my lesson and I avoid any confrontations, I just say sorry and walk away.
My understanding is the Brit was unhappy with the way the Thai drove the car and banged on his car a couple of times . That was enough for the Thai to chase after him and kill him in cold blood.
I still remember one episode inside a shopping mall when I was unhappy with the service of one of the sales staff and I gave him the finger and walked away. That was 20 years ago and I was a newbie in Thailand. He came after me and chased me for 1 hour, up and down the mall, I had to run for my life. I managed to escape and never set foot inside that mall again .
So never provoke anyone, even if it looks innocent it could be your last day.