Any good and reliable preown car dealers to recommend in Bangkok?

Can anyone share notes or tips on the process of buying a used car?

Can I hire someone to check the mechanics? Worthwhile?

Any gotchas to look out for? (Such as unpaid instalments?)

With going to a dealer or not?

Steps? (if they're more complex than find car, go to DLT to transfer, take blue book, send bank transfer.)

What else don't I know?

I'm on an Elite visa looking to buy something like a 2015 Prius. (Am not vegan, but do wear sandals.) Huge thanks