@Lisa **************************
and as you can see,
you could CONTACT your air carrier and see if they will let you fly with onward travel dated further out than your entry stamp will be & once you're here get the 30 day extension
OR
you can buy a single entry tourist visa from the thai consulate in your country before you you come. <- which covers the proof of onward travel requirement your airline might have AND gives you the time you want here without going to the immigration office for an extension ๐