No rego means no insurance and as a foreigner not a good idea. Same with driving/riding license. Almost none of my thai friends have one and my wife has never had one but, as a falang, it is essential to have license and rego. Laws are enforced 100 times more on foreigners.
yes there is a whole industry based around circumventing Thai law in this area as well as property ownership. Eventually the whole house of cards will come crashing down.