@Erin ******
, in my experience, getting the extension was not as quick as people always say. I am in Chiang Mai, so perhaps it could be different in another city. Bring with you the TM30, check that all the information in it matches, print a copy of your 2-month stamp on your passport and another copy of your main page with the photo and information, 1 passport-type photo with a blue or white background (I cannot remember if it's 3cm x 2cm.. you can see this on the form TM7), your physical passport, and 1900 baht. Don't forget to bring your own pencil because you will need one to complete another form, the TM7. You can get this one at the immigration office, usually at the entrance; grab one and fill it out, do all this with enough time, dont wait until last day.