Hm,...When I cam to Thailand, more than 30 Y. ago, it was a well known fact that Buddhist temples were a refuge for criminals as well as for real Buddhists. Criminals on the run took refuge in temples far away from the places were they operated and became monks !. At that time they could change there identity while been monk. this has changed years ago, as the practice was widespread. Now Monks have a special ID card. But once and a while you still can see monks with Tattoos to be meant to protect them against knife or gun attacks !!!, mixed with Buddhist tattoos !!
PS: The photograph is not mine ! It's just a example I Down Loaded long time ago