There is no visa to extend, as it expired on the date stamped in your passport. You may have other options. What happens depends on the individual officer and his superior.
The TM-60 multiple entry visa can be obtained in your home country. It's not an option within Thailand. You can change to a Type O or OA visa after arrival.
You can't get a work permit and teach English on a tourist visa. You can change visa categories in country, but to teach you'll need a school to sponsor your visa and work permit.
it 5 years for 1 day if you're CAUGHT by police and detained. If you leave via immigration without getting caught by police you get fined ฿500 per day with no detention. All this is common knowledge, as are ways to avoid having to worry about it.