I'd say it's complicated. Could I figure it out and do it myself? Sure, but retirement means you stop taking on new time intensive and stressful projects! Instead outsource to those that know the latest rules and can get it done properly. I use my agent for anything immigration related.
Reiterating others that suggest a visa agent. I consulted with one when I first started thinking about relocating to Thailand. Now I use that agent for anything related to immigration. Saves a lot of confusion and is stress-free. Very reasonable cost considering I place a high value on my time.