As most replies mention, better apply for an extension (30 days). It never looks positive to have an overstay in your passport. It's not worth the couple of Baht that you are saving on an overstay fine.
100% correct. Take a visa office with a foreigner to apply for your Retirement Visa. It wll cost between 28.000-32.000 THB. I've been applying the last 3 years myself. Cost me 1.900 THB and
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day work with banking docs, immigration papers, copies and immigration office