yes but if your not paying tax at home, you won't have a bank account there, so your probably going to be at the maximum tax. Unless your extremely poor, which seems unlikely.
no but I saw it on the Thaiger News. Remember the Thai language doesn't always translate well. Unlikely the tax agreement is only federal government workers... The Thai government was clear that this isn't a tax grab for retirees to be concerned about. There are some grey areas!
My onward ticket has always 5 months from my arrival. I was told by a Thai Consulate they don't care what your outbound ticket is because anyone can change this at anytime....