Buy one with a plate already.. Just takes so many problems off the table unless yoru looking to only trail ride and not tour.
Easy to find plated options range form KLX250s to DRZ400's.. More rare would be stuff like smaller 2 strokes (CRM250s WR's KDX250s) which do pop up plated once in a blue moon. Or larger 4 strokes like dr650's XR650's etc suited to touring.
Thailand is probably still one of the easier countries to find something. mocyc.com has a lot of bikes on it but be warned that many have had very poor maintenance and its not unusual for bikes to be modified to bodge in unintended parts, that when they fail you simply cannot repair (I found mazda 323 main bearings cut down in a cbr engine.. They had cut the engine cases out meaning the bodge, which didnt work, had ruined any hope of getting the right parts for repair).
Do you want to trail ride, or tour, or a bit of both ??