I have seen many different posts about purchasing a vehicle from different province and not being able to change title in different province. It was very easy process. I purchased a motorbike in Chiang Mai from a buyer who had all the documents needed from original seller in Bangkok ( signed Thai ID, transfer papers, green book and power of attorney). He never changed the ownership. I Went to Chiang Mai DLT on a Monday and with paperwork from Bangkok to have changed to Chiang Mai. They made me have bike inspected there and told come back Wednesday for new plates. They gave me a new tax sticker for Chiang Mai with same expiration as old one from Bangkok. Insurance was still valid from old owner so did not need to purchase. Small fee and issued plate. 2 trips to DLT and done in 3 days. Changing ownership and province is not an issue.