@Cody ********
, your understanding is incorrect :/
There is no such thing as a 30 day tourist visa :O
IF you showed up here without having bought a visa from a thai consulate in your country before hand and were stamped in for FREE for 30 days you were stamped in on what's known as a 30 day visa exempt entry.
Be that as it may, you can go to the immigration office and get a 30 day extension for 1900baht at the immigration office.
After that you either go to a thai consulate in another country and BUY a single entry tourist visa OR you go to a border, stamp out of thailand, stamp in&out of another country and then back into thailand to get a new 30 day visa exempt entry stamp