I live in Chiang Mai and have been stopped (not recently) for not hearing a motorcycle helmet. There are also roadblocks weekly (lately daily) on highway 121, with the police looking for Burmese. Last nite, on highway 121, between the superhighway and 1006, the police were stopping older vechiles and checking the exhausts. It looked like a rinkyding operation, with them gunning the engine while a contraption was attached to the muffler. If your vechile did more than a 45 level (I have no idea if this means carbon particle or what), you got a ticket, which was payable immediately. Driving a 1998 truck (in good condition), it registered 53.5 and I had to pay 500 bath (the Thai sitting next to me along side the road was fined 200 baht). I will have my truck looked at and fixed, if necessary. I will probably also avoid driving on 121, especially from 4-6 P.M. Its the closest way to pick up kids at school but I can take superhighway around the other direction to 1006 (it will probably add 2 miles to my trip). Has anyone else been stopped for this offense? And what other things do the police stop for?