Since you are from the US you will get a 30 day visa exempt entry not a 15 day visa on arrival that only a few countries qualify for.
You can apply for a non-o visa based upon retirement at immigration and then near the end of the 90 days it allows you can apply for the one year extension.
Requirements for the non-o are here. https://bangkok.immigration.go.th/wp-content/uploads/2022C1_09.pdf