I recommend to give the transfer job to some car dealer. They have all forms in their shop and know what's requiered in copies. Especially if you buy from a farang. For my motorbike they charged me 100 thb since i bought from private and not from them. Even if you need to pay 1000,- it's worth it.
I had to pay 1600,- thb! It's up to the IO and the connected agengy. The Immigration doesn't provide Visas at all. They send you to the agency next door. At least at Cham Yeam check-point it's handeled like this.