I assume that there are statistics available by the Navy somewhere but they probably don't like to publish it much as it may hurt tourism or give the country a bad image. Of course with our current prime minister, image is everything. However I think accident is relatively rare as it tends to get talked a lot locally and there don't seem to be too many stories about dive fatality each year, probably a few per year I would guess. Now, with the number of divers in Thailand, I don't know if this would consider too high, normal or low. Consider the number of rather shady and not up to specs boats with all the neccessary first aide, life supports etc there are in Thailand (although the boats on average are better equiped than they used to and it is improving all the time).