First of all, this website maintained by the Phuket Immigration Volunteers is an invaluable resource:
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How to navigate the site might be non-obvious. The icon with the three horizontal bars on the left-hand side of the page allows you to go to a different part of the website.
possibly even easier if you use the drive through at Phuket Town immigration. Friends assure me that all that's needed is your passport and your previous 90 day report receipt that shows the next due date. I can't personally confirm this as I always do online.
I hope everything gets back to normal as soon as possible. But I've thrown out my crystal ball because it has proven to be defective. ;-)
But my point was that there are sound reasons to prefer a Non-O over the Non-OA just because of the Thai health insurance requirement that Thai Immigration has imposed on the Non-OA but not on the Non-O.
And, unfortunately, the pandemic has made the Non-OA even less desirable now because due to quarantines and such it is now much harder to leave and re-enter Thailand, which is necessary to take full advantage of the Non-OA (you can get almost two years permission to stay out of a single Non-OA visa if you do a border run just before it expires after the first year).
In the past Non-OA did have advantages over Non-O, but with the ongoing insurance requirement and the pandemic making entering Thailand more difficult they have all disappeared, in my opinion.
My point is that if you are going to be in Thailand for years and years, a Non-O lets you do that without purchasing Thai health insurance approved by Thai Immigration, while a Non-OA does require you to do so.
The advantages of having a Non-OA disappear if it is not convenient to do a border run (air or land) to get another year extension of stay. And getting another Non-OA requires you to obtain it from your home country (US) which is certainly not convenient to do so under normal circumstances, much less during the pandemic.
If you are staying in Thailand why would you prefer a Non-OA visa over a Non-O visa when the Non-OA requires that you purchase something the Non-O doesn't?
A story of two people Oscar and Andy. Obviously, everyone now requires Covid insurance to enter Thailand so I won't make that part of the story.
Oscar gets a Non-O visa in America (if that is possible for purposes of retirement) and arrives in Thailand. He opens a bank account and transfers 800,000 baht equivalent into his Thai bank account. He applies for and receives a year extension of permission to stay (for 1,900 baht). He can do the same year after year without ever needing to leave Thailand (he can if he wants to, but doesn't have to) nor does he need to ever purchase health insurance that is approved by Thai Immigration (again, he can purchase health insurance if he wants to but is not required to do so).
Andy gets a Non-OA visa in America. He must have health insurance that satisfies Thai Immigration (something Oscar did not need). He arrives in Thailand and is given permission to stay for one year. At the end of that year, he has to either apply for an extension to stay (just like Oscar, but unlike Oscar, he has to continue to purchase Thai health insurance that satisfies Thai Immigration) or he has to leave and re-enter Thailand (currently that would require a 2-week stay in quarantine). He would have to fly somewhere where there is no quarantine in effect so he could avoid a 2-week quarantine in that destination and then fly back into Thailand and undergo another 2-week stay in quarantine. After going through that process (not exactly convenient to my way of thinking) he would again have another year of permission to stay in Thailand. After that year he would either have to do exactly what Oscar did (except unlike Oscar he must still purchase Thai health insurance) and get an extension of stay by opening a Thai bank account, funding it with 800,000 baht, paying 1,900 for the extension. Or, he would have to go all the way back to the US to obtain another Non-OA visa and repeat this whole process again (of course, involving another 2-week stay in quarantine in Thailand plus any requirements for that the US might impose depending of course on there being any airlines willing to carry passengers from Thailand to the US and back. For as long as Andy wishes to stay in Thailand he will forever be required to purchase Thai health insurance (something that becomes incredibly expensive or impossible the older you get), something that Oscar will not be required to do.
I'm guessing Oscar doesn't think Andy has a more convenient way of staying in Thailand. ;-)
The advantage of the Non-O, if it can be obtained in America for purposes of retirement, is that it does not automatically come with the requirement for health insurance that accompanies the Non-OA visa. Therefore, the cost and convenience of a Non-O visa may well outweigh that of a Non-OA.
My understanding is that with a visa you can enter Thailand without having proof of onward travel (POOT), such as a return air ticket. Whether your airline will let you board the flight to Thailand without POOT is another matter best checked with your individual airline. If you are expecting to use the visa-exempt entry program I believe Thailand requires POOT in that case and your airline would almost certainly also require it.
If you are inside Thailand and your visa expires, you don't care because you would have been granted permission to stay when you entered the country (see the latest Thailand entry stamp in your passport stay until date) that doesn't go away just because your visa expires.
If you are outside Thailand and your visa expires, then you aren't going to be able to enter Thailand until you get a new visa that is not expired (or you can enter Thailand if you qualify by nationality for the visa-waiver entry).