It's cheaper to get a 60 day tourist visa from your country, 1900 baht extension,+ photos and photo copies and you could be in immigration for hours in Thailand. Just not worth the hassle
They will let you off with 1 day overstay usually, but even if you have 2 or 3 days there seems to be no real hassle, speaking from experience I have never had a problem, the agents always seem pleasant