What are the options for extending a visa exemption in Thailand, and where should I apply?

In Bangkok you can apply for a 30 day extension when you have 45 days or less left on your current stamp <- meaning you could have applied any time after Nov 29th 😮 ) so any time now

NOTE; you don't lose time going early, they add the 30 days to your current expiration date 🙂

you would go to the Immigration office located at IT Square Laksi Plaza (3rd floor) that's where visa exempt extensions are issued. It is the ONLY office you can use in Bangkok.

There are copy/photo shops next to the immigration office where you can get the required copies, passport sized photo and the forms are available at the immigration office as you enter the area.

You need proof of having a TM30 filed (notification of foreigner in residence receipt) showing you're registered as staying at an address in bangkok.