What are the key details I need to know about my Non-Immigrant O-A retirement visa in Thailand, including reporting requirements and re-entry permits?

Also for the 90 day report you need to work it out yourself. The day you get stamped in by immigration is day 1 so 89 days from then

Nothing in Thailand automatically renews. You should have done some more research on visas before you applied for one, so you would at least know how the visa you you were applying for worked.

A non-OA visa is valid for 1 year, and obtain it by showing money in your home country and a 1 year insurance policy.

Every single time you enter Thailand during the validity of the visa, you will be stamped in for 1 year, or until the end of the insurance you show the immigration officer.

If you leave and re-enter Thailand just before the end of your visa validity date, along with a new year of insurance, you will be given a final 1-year entry stamp, basically getting 2 years out of your visa.

If you decide to leave Thailand during this extra year, you would need to apply for a re-entry permit as you no longer have a valid visa and your stamp will be made invalid when you leave the country without a re-entry permit.

After year 2 you would need to return to your home country and apply for a new OA visa, or you could apply for a 1-year extension in Thailand, but you should not do this as you will be required to show 800,000 baht in a Thai bank account AND the same high level of insurance. You should either go get a new OA visa with money shown at home, or leave Thailand and let your stamp expires and then get a new non-O visa which does not have an insurance requirement but does have the 800,000 baht in an account requirement.