TLDR : Answer Summary
To extend your METV (Multiple Entry Tourist Visa) in Bangkok, gather the necessary documentation, including copies of your passport's ID page, visa page, 'Admitted to Stay' stamp, TM 6 departure card, and TM 7 application form. Prepare the fee of 1,900 THB. Upon arrival at the immigration office, present your documents at the queue counter for section J-2, where you will receive a queue number. Wait until your number is called, then submit your paperwork and fee to the officer. After processing, you will be notified when your extension is complete.