I found immigration in Bangkok to be very organized and professional. They do everything by the book. I did my OA extensions there for 6 years and never had a problem. I found no need for an agent.
Another perspective is to go as early as possible which would be 30 or 45 days depending on your immigration office. Ask your question and then bring everything that is easy to do. It’s a lot easier to bring too much than not enough. If they don’t want it they won’t take it. If you don’t have something then you have plenty of time to get what you need and return another day if that is necessary. Take notes. Next time you will know what you need to know.
The US embassy no longer provides residency certificates.
I was able to get both my Thai drivers and motorbike licenses using my California drivers license. No IDP. I didn’t have to take a road test or the written test. This was at the DLT office at Bang Chak, Bangkok.
I got my medical certificate at one of the small medical clinics.
I came to Thailand on an OA visa in 2017. In 2019 Thailand imposed an insurance requirement to this visa. I have Thai insurance and had my OA for 6 years. I suggest that you carefully review your insurance coverage before committing to an OA. Also, I am not sure if the insurance you use to get your original OA visa will qualify when you do your OA yearly extensions inside Thailand. I know my Thai insurance did qualify.
Personally I recommend that you pursue an O visa for yourself. There is no insurance requirement with an O visa. I am not suggesting you shouldn’t have insurance but you may not want to tie it to your visa.
For both the OA and O visas you eventually get to the point of extending (not renewing) one year at a time. The process and cost of extending both visas is the same except for the OA insurance requirement.
I actually switched from my OA to a 10 year pensioner LTR visa. The LTR visa is offered through the Thailand Board of Investment (BOI). Google BOI LTR to see the requirements for this visa if you are interested. There is an insurance requirement. No 90 day reporting requirement. No yearly extensions. You need $80,000/yr passive income.
I agree with others that the air quality in Northern Thailand is notoriously bad for part of the year.
My US bank won’t process wire transfer requests on weekends and holidays. The fastest I get wire transfers sent from the US and then deposited into my Thai bank is about 18-20 hours.
Once my US banks the money then you have to wait for your Thai bank to deposit it into your account. That also might not happen on weekends and holidays.
The drivers license and motorbike license are two different licenses. Get them at the same time. I got the drivers license one year and then the motorbike license the next year. Since the first license is a 2 year license I ended up at the Bang Chak office 4 years in a row. Watched that movie 4x.
The 1 year permission to stay stamp comes from the Immigration officer when returned through the airport. 1 year extensions were done at Bangkok Immigration.
I arrived with an OA in February 2017. I took a trip to Cambodia in November 2017. Like you, not understanding the visa, I went to extend in February 2018. Immigration told me to come back in November 2018. From then on I extended every November.
When they implemented the insurance requirement in 2019 I always synced my insurance dates with my November extension date.