First time doing this and needless to say a bit anxious about the outcome. I followed the instructions on the US Embassy Bangkok website 100%. Double, triple and then quadruple checked the contents and for accuracy. Satisfied I'd gotten it all prepared correctly. Dropped it off and the Thai Post in Jomtien on 8 Feb. The tracking showed it was delivered and accepted at the US Embassy by the security guard on 12 Feb. Then the wait begins. Much to my delight it arrived yesterday 8 Mar, exactly 1 month from sending. Everything was pretty clear and easy. I paid for the Courier Pass Back Service online with my credit card. It was quite simple.
EXCELLENT Service all-round.