I got my LTR before there were any tax rule changes. Taxes were not a consideration in 2022. It turned out to be a side benefit recently. The cost over 10 years is low and the convenience factor is high.
Yes, federal pensions are not taxed depending on the dual tax treaty with your country. If you have any other types of income though then you might have considered the tax implications. For instance I have both a work pension (potentially taxable) and US Social Security (non taxable). I certainly don’t know the OP’s full financial circumstances.
The LTR is still a good visa and I am suggesting it as something to look into. If it doesn’t apply then there are other alternatives.
I’ve heard others say that they have some type of Medicare supplemental insurance that they can use overseas. I don’t know the details myself. I only have Medicare Part A and I can’t use this outside the US.
I used to have an OA visa but I got it in 2017 before there was an insurance requirement. I don’t know what insurance is acceptable when getting an OA in your home country but I highly doubt Medicare or any supplement would qualify. I have Thai insurance, Pacific Cross. They want you to have insurance you can use in Thailand. Eventually you have to get 1 year extensions of your OA and then you will need Thai insurance to do that. To use non-Thai insurance for the 1 year extensions you have to get your insurance company to sign a document that says their policy conforms to the Thai requirements. Mostly I hear that insurance companies will not sign the form.
I would not count on Medicare helping you with regards to meeting any immigration requirements or paying for any medical treatment in Thailand. If you want health insurance in Thailand you need to pay for it yourself or self insure.
Like I said, I have little risk of paying any Thai tax and as it turned out I learned of some advantages to my US tax obligations due to the Thai-US tax treaty that I wouldn’t have known about if I hadn’t talked to the tax firm.
The tax rule change came into effect Jan 1, 2024. It has always been the case that you become a Thai tax resident after 180 days. Don’t want to file a tax return? That’s up to you. Good luck with that.