Can I use a certificate of residency from my home in trat to get a thai driving license  in another province ? Have to go Kanchanaburi for a week, and thought I would get it there. Also you bring your own motor bike for the test correct ? 

It does of course depend on the DLT, but the answer will most likely be no, they won't accept a certificate of residence from another province.

You will have to be registered as "resident" in Kanchanaburi either by yourself or hotel, you could get a residence report based on this from Police.

I did this in "another" province from where I was living to get new DL, though that was a few years ago & with the constantly moving goal posts here who knows if it would still be accepted.