BMW riders with Chinese registrations? Might be one of the last times you'll see any Chinese motorcycles in Thailand since new rules to go into effect either late next month or in June will ban Chinese motorcycles and campervans, while cars will require 10 days advance notice, itineraries, driver's licences and driver orientation etc. after which the car will only be allowed to travel in the border province entered; must also exit through the same border control too. So no loops either, for example, entering at Chiang Khong and exiting at Mae Sai, despite Mae Sai being in the same province.
Then again you can't blame the Thais - too many Chinese have been bringing their vehicles in, in the absence of an agreement with Thailand, many causing accidents and near-accidents. Going in the other direction is near impossible. Now the Thais will have the last laugh because the Chinese are about to experience the same coming here.