IF you entered on a 30 day visa exempt entry (back before the lock down) you go to the Muang Thong Thani Immigration office Counter K.
You will get an under consideration stamp and then go back on that date to get the extension inked in. IF your embassy doesn't issue a letter you don't need it.
The wait in Section K CAN BE lengthy, so it is recommended you make an appointment on the online booking system
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