I think a doctor in the U.S. will need you to at least claim you’re physically in the U.S., and in a state where they’re licensed to practice medicine, in order to legally have a virtual visit with you to prescribe the medication. Otherwise, they’re practicing medicine internationally. A virtual medical service like Galileo will be prickly about that. A solo practitioner might not even bother asking. But, either way, it’s your supposed location on the day of the visit, not your citizenship, that matters. If you’re a U.S. citizen physically in Bangkok, a doctor might cancel the appointment. If you’re a Thai citizen physically in the U.S., no worries. So, maybe try to do a virtual appointment, or even an in person appointment, with one of the specific doctors or services the others are recommending here. (A service like Galileo or One Medical would be fine for something run of the mill, like metformin, but might have lots of questions before prescribing rapamycin, and insist on lab work first.)
I think the doctor can send the prescription to pretty much any pharmacy in the U.S. for you to pick up, or to an online pharmacy like Amazon Pharmacy for shipping to anywhere in the U.S. But, either way you’re going to need to either go to the pharmacy in the U.S. to pick it up, or give the online pharmacy an address in the U.S. You could probably use a PO Box or virtual mailbox service for that, and I think Bounce gets good reviews for accepting packages in NYC. If you google “package receiving service” that might help you find a good option near the border.
So, maybe check to see what the price is at a chain like Walgreens (you can probably find one near the border), and compare it to what Amazon Pharmacy and the online pharmacies other folks are recommending, and then you can decide whether to pick up your pills at a Walgreens, or have them shipped to a package receiving service.
If the doctor authorizes multiple refills, I think Amazon can just fill them all up front if you’re paying out of pocket, as opposed to waiting for each 90 day round of pills to run out. I’m not sure if that’s standard everywhere. (Insurance companies make you wait for each 90 day bottle.) Alternatively, once you have a prescription, Jase Medical is a compounding pharmacy that will do a virtual appointment to authorize a one-year supply, and ship it to an address in the U.S. (so, a package receiving service). I’m not sure if they carry rapamycin, or how their prices compare, but if you can only make one visit a year to get your meds, they might be a good option.
Hope that helps!