Jayboy the Auctions ---IMO are a good place to get feel for the price & to buy. Take a Thai with you --(in Issan) usually the first day its offered country wide by Video--to dealers, the top price that they offer will be what it starts at the next day for everyone to bid. I have brought there twice---- surprising how new some of the cars are. Other then that " Baht sold" for English -and - ขายดี K̄hāy dī = sell good in Thai both very good for cars bikes real estate rental or buying.
A tip for verifying the age--- Pull the front seat belt fully out on the bottom of it will be sewn a white sticker with the year on it