Do I need to go to an immigration office in Bangkok for my visa extension or can I pay at the airport for the overstay?

So you know... Having an OVERSTAY STAMP in your passport can effect your ability to enter other countries as well as Thailand.

Just yesterday an expat with an OVERSTAY stamp from Thailand in his passport was denied entry into Singapore. Like you they were only a few days OVERSTAY...Other nations do look at your passport when you arrive.

in Bangkok to get a 30 day extension on a visa exempt entry you DO NOT go to the main immigration office in the Government Complex, BUT you go to IT Square Laksi Plaza 3rd floor to get the extension

There is no 30 day visa 😕 So we'll go under the premise showed up here with NO visa in your passport and got in on a free entry stamp for 30 days <- which is NOT a visa 😉

The price to get a 30 day extension on that is 1900baht at the immigration office and the price to just do nothing and pay the 4 day overstay at the airport when you fly out is 2000baht (500 baht a day) AND you get a big overstay stamp in your passport.

Personally I'd say just go to the immigration office and apply for the 30 day extension for 1900baht (which you can do any time as they add it to your current expiration date). That avoids the overstay stamp