you make an appointment with the American Citizen Services Office of the US Consulate here in Bangkok, then go apply for a new passport. (mark the box stating you want the large 52 page passport because it's the same price as the small one when you renew overseas).
It takes about 10 working days BUT we got Christmas and New Years just around the corner. They send you an SMS / email when your new passport is in and you go get it. They give you a letter to immigration's asking that they transfer any stamps and the cancel your old passport when you get the new one
This tells you what to do to get a new passport in Bangkok
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