My license expires in November this year. How long before November can I renew it to a 5-year license?

I renewed mine here in Chiang Mai recently, and the process went smoothly. I got the 5-year license about two weeks before my old 1-year license expired.

I had been informed - and I think it was on ThaiVisa - that your old license had to expire before you could apply for a new one. Not so.

My wife tells me that it can be done a month before expiration.

That was my experience.

You want to try and time it so it's shortly after your birthday, that way you get nearly 6 years.

At the Sukhumvit branch in Bangkok it's up to 60 days before the license expires for a 1 year licence, and up to 90 days before the license expires for a 5 year license.

You want to try and time it so it's shortly after your birthday, that way you get nearly 6 years.

Correct, you will get 5 years + time until your birthday.

Permanent driving licenses in Thailand always expires on your birthday.