If you take a look at
https://www.gt-rider.com/bikes.html#BUYINGABIKE
it might clear the air a bit
Thai people require an ID card plus a copy of their house registration paper to register a vehicle in their own name.
Foreigners need the "same" - confirmation of ID and local address. This means a copy of your passport and a letter from your local immigration office or consul confirming your Thailand address.
To get this, you should have a 3-month non-immigrant visa, suggesting that you live in Thailand. However there are exceptions to the rule and the Chiang Mai immigration office does issue these letters.
Note too, that the originals must be presented at the vehicle licensing office, not photocopies.
It is possible to take a vehicle out of the country, if it does not belong to you, but is in the name of another person. To do this you must have permission from the vehicle owner to export it. There is a standard form you can use for this. Click here (
https://www.gt-rider.com/docsgallery/FrameSet.htm) to see what it looks like.
Under this system, it is possible to buy a motorcycle in another person's name and ride it out. To do this, you must have signed copies of the real owner's valid / current (not expired) Thai ID card and Thai house registration.
This normally works, however it is open to the duty Customs officer's personal discretion; and if you have a communication problem or a personality clash (I have good experience of this) it might not go down so well. For foreign riders with Thai registered bikes this is a not uncommon problem on the border.
One of the Customs concern is that the motorcycle may be stolen, or may not be returned. So, be patient, tolerant and understanding of the system.
Don't believe the shop, where you buy the bike, that you only need a receipt & / or a photocopy of the bike registration. You won't get out of the country. It is no fun riding all the way to the border, to discover that you've wasted your time and money & probably stuffed up your holiday.
Davidfl
Keep The Power On