Here's the address to mail in a 90 day report for Bangkok,
You need the paper they gave you that says when your report is due, a filled out TM47 90 day report form, copies of the data page of your passport, your visa stamp, your last entry stamp, your current extension and your TM6 departure card. You also enclose a self addressed stamped envelope so they can mail your receipt back to you
Send it EMS (tracked mail) to this address;
ATTENTION 90 Day Reporting
Immigration Office Division 1
Chalermprakiat Government Complex
120 Moo 3 Chaengwattana Road Soi 7
Thungsonghong, Laksi Bangkok
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