Just did my intl lic yday (505 baht). 2 x passport photos, Thai 5-yr driving licence, passport. residency cert fr immigration. Nice to bring your own photocopies along, but they did their own anyway at DLT Chonburi office. For Ptya residents: intl lic not avlble in Banglamung DLT, you need to go to Chonburi HO.
Res cert 300 baht, no docs required, just pp and filled out form (avlble at the office, in my case Chonburi/Sri Racha. 15 mins, done. No ID requirements (bills etc).
Intl kic is valid for 2 yrs + in my case (exp on bday in 2025, so got 26 months of validity out of it).
For an extra 55 baht they updated my 5-yr TH drivers licence, new passport number, new photo (taken by them at the DLT office), = new plastic card. Same expiry date as old one.