If you are a seller, the lady at the last but one shop at the entrance to the car park to Banglamung LTO will do all the paperwork. Take all the necessary paperwork, and she will sort the documents and for a couple of hundred Baht will sort out the paperwork, and you can depart the scene. Having bought and sold various vehicles over the years - never had a problem. A buyer will have a bit more bureaucracy to sort out by which time you are miles away. May not be the same deal at your local LTO, but I bet the same solution is available at a price at any LTO.
Passport, house book (yellow or blue), reg for the car/bike, and that's about it at Banglamung LTO. As usual, the documents and copies will vary