Now that I am thinking about it, I wonder if the driver just totally made up the part about your bag hitting his car? Did the police see that on video? Is your bag hanging off your bike in such a way that is possible? It is no excuse obviously for the man to hit you later but since Thais hate to admit fault he had to think of some lie.
I was hit from behind while slowing, in the day, with my turn signal on, my lights all worked, and two motor bikes driving together, one or both of them hit me, then they both fell down. Then they got up from the street and jumped on their bikes and drove away! Every Thai person I told about this, advised me to make a up a lie for my insurance company. They would say I should say I got hit in a parking lot while I was shopping. I think they all thought I was making up my story to some degree. I would ask them, why should I lie, I didn’t do anything wrong, and it might be obvious I am making up a story? It was just a repair to my bumper about 18 years ago, so it cost maybe 4000 or 6000 baht I think, I just paid it myself.
I never asked people what I should do either, they would ask how my car got like that and I would tell them and next sentence would be their suggested lie, every single time!!
Maybe the guy was just drunk. He thinks this story is better because he was too dumb to realize he was admitting to attempting to murder you. If he really did that I think he would say his brakes failed.