You got two choices
1 - Come in 30 day free stamp (visa exempt) then go get the one 30 day extension you're allowed at the immigration office where you stay for 1900baht
2 - BUY a single entry tourist visa from the thai consulate in your country before you wing your way here via the online eVisa website and when you enter you'll get stamped in for 60 days
You apply, upload your documentation, pay all online, they will email you the PDF file that is your visa. Print that and present it to the immigration office when you stamp in.
Those are your choices to stay the time you want
Here's the eVisa website
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