Buying a used vehicle, blue book signed by the owner is enough to transfer / register under new owner?

Thanks for the help.

Depends on year etc. Let an agent deal with it, no muss no fuss, cheap (about (800 to 1200b depending on car model and age) and easily done to have someone who knows what to do handle it.

you'll also need copies (and original?) of buyer and seller's ID/Passport, if foreigner (buyer or seller) need Residency Certificate or Yellow Book (maybe not if have Work Permit). i am not sure if all DLT offices are the same but some require the car to do a VIN and engine number check at the DLT, and you need to get that certificate before able to transfer.

Maybe overkill, but better to take the buyer with you, so can sort out any transfer problems before paying for it. In Thailand the legal owner of the vehicle is the name in the Blue Book, not any other signed document. Can also, as Warp Speed suggested, get an agent to transfer for you but you will need seller to sign a Power of Attorney.

for the forms you may need, i think on the link below the 1st doc is for transfer and the 4th one is for Power of Attorney (POA)

http://www.dlt.go.th/th/eform/index.php

a rough English guide

http://vigportal.mot.go.th/portal/site/PortalMOTEN/menuitem.1dc3170181d739ec38537ff5506001ca/