, Bangkok was never a part of the Sandbox program. The fact that these (3rd party) sites are calling it sandbox is misleading, because all you were doing is either test and go, or 7 day quarantine. Only Phuket, Phi Phi, and Samui area (and maybe Krabi??) ever had a Sandbox plan.
So, you either booked 6 days under test and go program, in which case, the hotel arranged your testing. OR the hotel was under the impression you were a domestic traveller?
I think there was a period of about a week where people weren't given the form even though we were expecting it. I arrived on Dec 26th in Phuket (test and go) and was not given any pink slip, or anything to suggest a day 6 test, or where to get it done. Also, I was in Bangkok by day 6.
Yes, this is the type of letter that I got. As long as the hotel is Sha +. I didn't see the designation on your letter, but that is something the Thai pass people/system should be able to confirm anyway.
, you need to have transport straight to the hotel from the airport. Testing is done at Phuket Airport. You need the hotel, insurance, and testing booked before doing Thai pass, as you need those receipts to enter into Thai pass.