What is the process for obtaining a Non-OA visa permit to stay in Thailand and how does leap year affect the duration?

Here is a confirmation of an OA visa experience and second-year permit to stay stamp, for reference. Nothing new, just showing how things work as expected sometimes. I got my one year Non O A multiple entry visa in the USA in November 2018 and entered Thailand at the CM airport the next month. I left Thailand in late March of this year to escape the bad air and 5 weeks later, upon my return to CM airport, I got a permit to stay stamp for one more year from the date of my re-entry. I again left Thailand on October 8th and returned at the CM airport on October 29th at 10 pm and once again got a permit to stay stamp, with the new date written in as October 27, 2020 - strange that it is 1 day short of a full year, but insignificant.

I pointed out to the IO that I had an OA visa and requested an additional one year permit to stay. He took 5 minutes to review my passport and info on his screen, but hardly talked to me, only asking me if I will be staying in CM. No other documentation or proof was requested of me. He simply handed me back my passport when done. I stepped past the booth and checked the stamp - all was good.

Next day, I went to CM immigration just before 12 noon and got my prior TM30 updated with a new stamp - no forms or other documentation needed; TM 6 in the passport was probably checked. Fast: in and out in a few minutes. A neighbor told me today the TM30 can now be updated at the airport upon arrival at a separate immigration desk, possibly past the standard immigration booths, , but I did not see that at the CM airport last night. Not a problem, as I live 15 minutes by bicycle from CM immigration and had the time today and need the exercise.

Thanks to the admins and other contributors for keeping us all up-to-date and answering all the questions!!

Update: I know I will need a rentry permit prior to leaving, if prior to the new Oct 2020 end date of my current stay permit, to maintain the validity for when I return.