Just south of Chiang Mai is the Chiang Mai Go-Kart Speedway. They rent go-karts and hold some organized Kart races as well as Motorcycle races. Really great is the fact that they also let you rent the track by the hour or the day at a ridiculously low price by Western standards. No worries about insurance or liability. just have fun and enjoy yourself.
My friends, Jeff, John, Jon and Justin talked me and Thim into a day of thrashing our motorcycles around. We had a grand time and no one was injured, which is a big plus.