How can I apply for a Non-O visa before entering Thailand without encountering issues with bank accounts?

RESOLVED: OK, I think it’s clear now, and I understand where I went wrong. The Non-O visa is available through the Thai eVisa website, but it’s not labeled as “Non-O”...it only shows up if you select the option to “stay in Thailand for no longer than 90 days” under “Retirement.” I had ruled that out because I want to stay longer, and I didn’t realize that you could apply for the correct 90-day non-O visa first, then extend it inside Thailand.

Since I didn’t see a way to apply for Non-O in advance and didn’t want to buy extra health insurance (I already have excellent coverage), I was planning to enter as a tourist and adjust status to non-O. Thanks to your guidance, I now see exactly how to apply for the Non-O in advance and skip that workaround.

Really appreciate everyone’s help. This was very useful! 🙏

ORIGINAL POST: Can someone help me resolve this catch‑22?

I’m a U.S. retiree with a pension and full health insurance. I plan to enter Thailand on a tourist visa (or visa‑exempt entry) and then convert to a Non‑Immigrant O retirement visa from inside Thailand. (EDITED: I'd enter as a tourist because I have excellent health insurance as a federal retiree, but I understand that the documentation is not sufficient to apply for an O visa online, whereas it's not a requirement to show my U.S. health insurance when converting in-country. If any U.S. federal retirees with FEHB coverage have managed to get around this problem, I'm all ears!)

I understand I’ll need 800,000 THB in a Thai bank account to convert to the O visa, but I also keep hearing that banks won’t open accounts for people on tourist visas. So how do you open a bank account before converting to an O visa...or, conversely, how can you convert to O before opening the bank account?

Would love to hear how others successfully handled this.