If you have an OA visa you will eventually have to get 1 year extensions of that visa here in Thailand. You will need qualifying health insurance to do that. The insurance you use to get the OA in the US may or may not qualify for an in county extension. At your age you may find it nearly impossible to buy into a new insurance policy. You should be certain about the insurance issues.
Alternatively you can get an O visa that will not have an insurance requirement for yearly extensions.
You’ve already been advised that you don’t need health insurance if you retire here on an O visa. I do have an insurance strategy though. I bought a 10 million baht policy from Pacific Cross with a 40,000 baht deductible. Health care is really inexpensive here and I have never spent as much as 40,000 baht in a year. A large deductible lowers the rate and I am getting an additional discount for not having made any claims. The insurance is there for a big health event such as an auto accident or a heart attack or whatever.
I know someone who got their 5 year Elite Visa at 44. He then had an 18 month gap until he turned 50. He chose to upgrade to the 20 year Elite at the old price. In your case one option is to get the 5 year Elite now and then figure out what to do about the gap later.
I had an OA from 2017- Jan 2023. I used the Bangkok Immigration office. Both the O and OA 1 year visa extensions have identical financial requirements. The OA also requires a health insurance certificate.
The insurance and financial requirements are separate requirements. Find an insurance policy that qualifies but you still either have to deposit the 800,000 baht or work your way into the monthly income requirement of 65,000 baht/month.
I deleted this earlier but I think I should state it again more clearly - If you want to extend your OA visa after only the first year then you cannot leave and re-enter during the first year. Of course you can leave and you don't need a re-entry permit but when you return you will be stamped in for a full year (or end of insurance). You can't extend until the final year end stamp expires.
This is what happened to me. I entered at the end of February 2017 and took a trip to Cambodia in Nov 2017. When I went to extend my OA in Feb 2018 in Bangkok they told me to return in November. After that my OA was always due for an extension in November.
You don't need a re-entry permit for the end of first year bounce but you do need to return before the end of the first year while you visa is valid. During the second year you will need a re-enty permit for any travel outside Thailand to keep the 2nd year active.
If you are from the US, UK, or Australia then you must show 12 months of minimum 65,000 baht deposits into your Thai bank account. The deposits must show the the money originated from outside Thailand. They don’t care where you got the money outside Thailand. Typically this means US citizens use the 800,000 method the first year while they make deposits to their Thai account so that they can use the income method for subsequent extensions.
1 year extentions of OA visas require insurance and typically Thai immigration requires that you have Thai insurance. You need to make sure the insurance you used to purchase the original OA visa in your home country will also qualify for subsequent 1 year extensions. I had Thai insurance so I never had to do that but my recollection is that you needed your non-Thai insurance company to sign a document acknowledging that their insurance coverage meets the Thai requirements. Getting your non-Thai insurance company to sign that document is not always a sure thing.