Simple process of extending my license in Udon Thani myself. Agent's are asking silly money for what is essentially a couple of hours work.
Asked my guesthouse/hotel for copy of TM30. Went to the new immigration by the lake.office. Had 2 months remaining but old passport has been lost.
Very friendly people at the office. Printed out every single entry in and out of Thailand and put the info with an official letter linking my new passport. I didn't ask for this to be done along with the 2 letters for the licence.
Driving licence office. Limited English with my limited Thai. Showed a copy of the QR code for online learning. Loads of photocopies of everything, old passport, DTV etc. After about 45 minutes 5 year's provided. Can't remember the exact amount but I think ฿1200.
Initially I went to the wrong office but they checked everything and made more photocopies and sectioned everything off. Ignore agent's wanting silly money saying it's difficult. Overall I came across very friendly people during the simple process.
My friend got his first 2 year exchanging UK licence at the same time. No IDP required.