Well isn't it normal to wait until the police arrive and then they take pics, measure skid marks, whatever they do. They would probably take statement etc.?
Certainly he called the emergency services and they came, but according to the story, unless I have missed something, he then left for the airport.
Police do not always attend traffic accidents in Thailand, many times the rescue services arrive, take care of the injured, insurance company reps turn up and that's it.
He was a passenger, not the driver, no requirement for him to wait any longer than he did which was to wait to see the woman being treated by medics as the pictures show.