What documents are needed to extend a 30-day visa exemption in Thailand, and which immigration office in Bangkok should I visit?

To extend a 30-day visa exemption in Thailand, you need to gather certain documents including copies of the data page of your passport, your entry stamp, the TM6 Departure card, and a filled-out TM7 application form, which should have a passport-sized photo attached. For processing, you can visit the Muang Thong Thani immigration office in Bangkok.