It is very common that tourists overstay for a day. Mostly because people think 1 month equals 31 days.
If it's just a day you overstayed it's mostly down to the custom officer in front of you. They are more lenient at the international airports then the land borders If it's more than that, you pay. Simple.
The red stamp you get just says you paid your overstay fine. Absolute no problems. I got several of them.
No worries, Just go direct to the over payment counter and pay before you go through customs. Although it will be 500 THB per day. There are no endless lectures as Thomas Lindegaard Jensen suggests.
Easy, peasy, straight forwards.
But be aware, as somebody already mentioned, should you get in to a silly police check, you might get problems.
I'd recommend to go for an extension before you legal time runs out. Extension costs 1920 THB (+ 500 thb a day if you're already overstaying)
Of course you can - but why would one want to spend half the day bringing the PP to the embassy, baking away in a bus or taxi, then do the same the next day again?
At the same time, you could sit on top of Penang Hill (where it's nice and COOL) with a bottle of wine and enjoy the view?
Or go to the beach? Or, or, or .....
There must be a 1000 things better to do in Penang than melting away like ice cream.