Go to the DLT, get an appointment and the list of required docs. You will need a certificate of residence from Immigration and a doctors certificate from any clinic (100.- THB). If you don't have an IDP, a translation of your local DP might be required. Another requirement will be watching some video. I did it at my nearby driving school and payed 200,- for the certificate. That's it. Pop-In at DLT on date of appointment, make a reaction test and sight test, pay your licence (about 300,- for car and moto), wait again for the photo shooting, wait a last time to receive the licences.
For each licence you need 1 doctors certificate and 1 certificate of residence!
A Thai diverse licence doesn't allow you to drive in UK, means you won't be covered by your insurance driving a bike in Thailand. Seems to be a typo or a sh*t company.