I'd assume a medical certificate would still be required but does one need to provide a letter of residency again?

Yes you will have too.. I had to do it from swapping an old five year one with a new one.

I changed from one to five years last month - in Pattaya.

Both were needed.

Cheers guys, that clears that up

The main thing needed is the visa. Since I only have a tourist visa, my residency certificate is only good for the month. Hence, I have only been able to get the 1 year license for the past five years.

Not sure what the law is but my limited experience is they also use discretion over issuing a 5-year or another 1-year. Back the first time I was extending a 1-year (quite some time ago) they had told me when inquired while passing by (at a renewal processing office outside a hospital in Udon, not the main registry) that I'd get one year. Had my son with me when went in to do it the next day and same person that told me this then asked me if I live in Udon permanently, chatted with me a bit, and gave me 5-years.

One of my friends is on annual extension of stays (Non-O based on marriage) but spends only 4-5 months per year in Thailand. He's on his third straight one-year, having been told he could only get 1-year each time.

Perhaps that's a location issue though.

You only get 5 yr. renewal when 1 yr. is expired. Do it day after exp. date.

They only gave me another I year licence as I didn't have visa, only an extension, however, a friend of mine didn't even have his passport and was given a 5 year one from the same office in Khon Kaen. He gave them some old pony about his passport being at the consulate, or something and he was in and out in 15 minutes.

TIT, I guess.

You only get 5 yr. renewal when 1 yr. is expired. Do it day after exp. date.

I was specifically told to go 2 months before mine expires or I will not be eligible for a 5 year license......

So many conflicting replies / experiences but TIT lol

The main question was answered and that's whether or not i need another letter of residency or not, I'll just take all my documents and see what happens at the Nong Jok DLT.

If i get a year, i get a year, if i get 5 then I’m a happier bunny