CMBob

There are multiple reasons to get a Thai tax ID. (1) If you need it for work or other purposes, (2) If you hope to have your bank no longer withhold the 15% tax on interest (for the first 20k baht or whatever) and presuming your bank will honor that request (as some posters say has occurred), or (3) If you want to file a Thai income tax return to receive back the mentioned tax from the Treasury. I obtained a tax ID years ago and filed a couple of tax returns and got the withheld 15% back when it was worth bothering with it (haven't bothered in the last couple of years because the interest withheld wasn't much but may do it again in January as you can claim back 3 years worth). Would note that I attempted (2-3 years ago) with my tax id card to ask my bank (SCB) to stop withholding the 15% and they simply said "no can do." Maybe I'll try again.

I did at both Bangkok Bank and SCB 20+ years ago but, like you said, things have changed. This past fall, I tried to open a Bangkok Bank account with only my 45-day exemption and they said "no" (I had to wait until I converted to a Non-O). You could visit a couple of branches of whatever banks and give it a try but, if that doesn't work, you're only option (if they'll handle it) is to use an agent.

Yes, open early for applications this year. Opened Monday (17th).

At CM Immigration last (2021) October, I converted from exempt to a Non-O and, while they could see from the bank passbook copies that the 800k had been in there for several years, there was nothing in the passbook (SCB) that reflected the funds came from abroad (the funds were deposited 10-12 years ago and the passbook CM Immigration saw only covered the last several years). Perhaps I got a break because they could see that the funds had been there for many years and/or that they could see I had many prior extensions based on retirement and gave me a break due to covid. Not sure.

According to the translation I've seen of the current Immigration Act (BE 2522), it says that one must report one's address upon "completion" of a ninety day period." In the OP's case, he/she hasn't completed a 90-day time period when leaving on the 90th day. And, while I never concerned myself with calculating the exact time before, I just looked at a couple of my 90-day Receipts of Notification and indeed the next report dates are on the 91st day (counting the first day).

I realize you have no need for a long time to renew your US passport but currently the answer to your question is easily obtained by a simple review of the Bangkok Embassy website section dealing with passport renewals. To assist, I'll paste the following from the website: Q: What payment methods are available for use via Pay.gov? A: You can pay the $130 fee by electronic check/transfer, credit/debit card, PayPal, or Amazon Pay on Pay.gov. This amount cannot be altered. You must pay the fee in U.S. dollars.