I think most of it is down to the lack of a safety culture in Thailand. May be connected with Buddhist resignation to fate, if something bad happens it was meant to be.
There are no sanctions for bad road behaviour like in Western countries where killing someone in a collision leads to years in prison and massive insurance payouts. Police do little enforcement except tea money speed traps and crash helmet fines.
No driver education, only minority have licences, bad signalling, follow too close, no giving way etc etc.
Until the Government makes road safety a priority, nothing will change. At the moment it’s just lip service with static checkpoints during dangerous holiday periods.
Get the police on mobile patrol, fix the broken speed and stoplight cameras, and teach the kids road safety instead of endless Thai history lessons. Make a difference and save some lives.