I lived in Thailand for 7 years, bikes are the poor mans transport, as such whenever there is an accident involving a motorbike it is always the other vehicles fault, no matter how stupid the bike rider. I once watched one of these funny film clip shows and it showed a woman riding a bike around the barriers on a train crossing point, the train hit the bike, immediately the Thais with me concluded that it was the train drivers fault.
Bike insurance is just about impossible to get.
If you are sitting in your car at traffic signals you are surrounded by bikes, they could go straight on, they could turn right, they could turn left, it is your job to avoid them, otherwise you are liable for medical treatment, repairs to the bike and loss of the riders wages. The price of all these doubles or triples when a foreigner is involved, two of my colleagues and their families had to be immediately taken out of the country after being involved in accidents involving bikes.
Cheers
Den