hi. Sorry not being negative with your situation. I went to get car licence same as you with UK license.
My gripe is the agencies offering licences for a fee. This allowing idiots on the roads no test, no training...causing deaths accidents. However where I am plenty of road users under age, no insurance etc.
a car licence transferred from an overseas existing licence is fine. But these companies providing a licence without you taking test or lessons is a good way to get people killed on the roads here.
You cannot work with a retirement visa. You can have a work visa but restricted to few jobs. But a bike? I wouldn't, it's dangerous in Thailand...but that's my view. The Thais could do with some good driving instruction however you may not be able too. The driving schools will not be to the standards you may expect and the fairness you may expect.