taxout

It depends on the particular company, but some will only send 2FA SMSs to "real" sim card-based numbers, not virtual numbers.

I was just able to log into my UM account from outside the US without a VPN. But yes, I had to reply ALLOW to an SMS first.

Schwab US requires you to keep a US residential address on your account. If you cannot do that, they will suggest you open an account at Schwab International.

Research this on POMS, the SocSec rulebook, and you'll find that a mailing address in the MA plan's service area is not enough. It must be your permanent residential address and the insuror is supposed to get documentary evidence of this when you sign up. Further, when MA plans do provide some international coverage they only provide it during your first two months overseas. In short, it's a non-starter for those living in Thailand. If anyone has any doubts about this, I'll let them do the research themselves.

Are you using the IRS Fillable Form 8938? Here's what the instructions say about adding accounts to Form 8938: "Form 8938, Statement of Foreign Financial Assets: Taxpayers may only attach one of these forms to their return. The form has two pages. Parts V and VI are on page 2. You may add, as continuation pages, a total 25 copies of page 2 (continuation pages)." https://www.irs.gov/e-file-providers/free-file-fillable-forms-program-limitations-and-available-forms#Form8938

(The Agoda app has an option to include taxes and fees in the room rates shown.)

The OP specifically says the person isn't a US resident. Case closed.

What "tax return" to recover the tax are you possibly talking about here. The OP says the recipient is not a US citizen or resident. No green card. Just your usual non-resident alien for whom withholding covers the US tax in full, no return required.

The US-Thailand Tax Treaty does not provide for reduced withholding tax on US social security payments, so the usual 30x85 rate applies. The treaty does provide, though, that the payments will not be subject to Thai income tax.

Never use registered mail! It's processed specially and can take an eternity -- yes, two months -- for delivery.

Since you're not a US person for US purposes, there's no Federal tax payable regardless of the amount you give or bequeath your son. But if he's required to file Form 3520 and doesn't, then there is a penalty based on the value received. Note the Form applies to bequests as well gifts. The elimination of accrued capital gains on bequests -- the "stepped-up basis rule" -- is one of the great loopholes in the Federal tax code, and one day it will be closed.

If you give him the shares as a gift, then when he sells them he'll be taxed in the US on any gain calculated on the basis of what you originally paid for them. But if he inherits the shares when you die he'll only be taxed on any gain accruing after your death. A foreign tax-sheltered account like an ISA usually creates nothing but headaches for an American because the US tax rules aren't written to deal with them. If the value of the gifts he receives from you a non-US person is more than $100,000 in any year he'll have to file IRS Form 3520.

Lucky you didn't get hit by a car etc in Scottsdale. Part A is actually pretty limited. Without Part B you'd still face crushing bills. Honestly, skip Part B only if you will never be present in the US. Otherwise it's like driving a car without liability insurance.

There's a kicker in the Part B premium calculation. Not to get into the details, but if you're in a higher income bracket your Part B premium will go up (and up). That's why the OP will be paying more.

Not only is registered mail ridiculously expensive but it's subject to special handling which slows down transit enormously. I had a registered envelope take two months to reach a bank in the US. Never again.