Q1) 180 days in a calendar year inside the Kingdom makes you tax resident and Thai tax law applies to any foreign sourced income. Whether you will actually pay any tax depends on your personal financial circumstances.
Q2) You register at your local tax office, bring your passport and proof of address.
By Thai law you are required to obtain a TIN within 60 days of receiving assessable income. Foreign sourced income is only assessable for Thai tax when remitted once you are a Thai tax resident. Not all foreign sourced income is assessable whilst tax resident, it depends on your source of funds and the wording of any exemptions in your country’s DTA. Everyone’s tax status will depend on their personal financial circumstances.
getting a second year out of an OA is NOT getting an extension. You are not extending anything, you are merely utilizing the OA to maximize your stay. You need to under stand the terminology. An extension of an OA requires funds in a Thai bank account.
no, he is talking about the OA, it is you who doesn’t understand this thread. The question was about obtaining an extension of the OA, this can only be done with funds in a Thai bank account.