Okay, IF you showed up here on a tourist visa that you bought from a thai consulate in another country before you arrived here and were stamped in for 60 days when you arrive IN BANGKOK you need to make an appointment to apply for a 30 day embassy request letter (and you need the letter from your embassy too) and you don't go to Chaengwattana you go to the Muang Thong Thani immigration location
You make the appointment on this website
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