I did it last year and simply followed the process outlined. You do have to send in your old passport, no way around it. Step-by-Step Mail-In Process Complete the Form: Fill out and print single-sided, then sign and date Form DS-82 (accessible via the U.S. Embassy in Thailand Passports Guide). You must provide your Social Security Number on the form. [1, 2] Get Photos: Prepare two identical 2x2 inch (5x5 cm) color passport photos with a white background. [1, 2, 3, 4] Pay the Fee: Pay the passport renewal fee online through the official government payment portal, and print out your payment confirmation receipt. [1, 2] Prepare Mailing Materials: Gather your current/expired original passport book, the completed/signed DS-82, the photo copies, payment confirmation, and a prepaid return envelope designated for Thailand tracking. [1] Mail the Package: Send your application packet strictly via Thailand Post or DHL directly to the U.S. Embassy Bangkok. Do not mail packages to the Chiang Mai consulate. [1]