@William ***************
seeing as you did NOT buy a tourist visa from a thai consulate in your country before you come here but just showed up and were stamped in free for 30 days you are NOT on a tourist visa (or a visa on arrival) but on what's called a 30 day visa exempt entry.
In Bangkok like
@Brandon ***********
correctly stated you would go to the Muang Thong Thani Immigration office
Here is where it is,
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