“As a holder of the "Wealthy Pensioner" category of LTR Visa, you are exempt from the Section 41 paragraph two foreign source income tax law, and therefore, you have no tax obligation in Thailand on any of the pension monies that you wire transfer from the US to Thailand. This exemption from the Section 41 paragraph two foreign source income tax law is provided to you under Royal Decree (No 743).
You also do not have to file any tax return in Thailand. For you to see this, see the attached PND95 Tax Return form. You'll see at the top of the form that only the "Highly Skilled Professionals" category of LTR Visa holders are required to file the PND95 tax return (not the "Wealthy Pensioner" category of LTR Visa holders).”
You need the 800,000 baht deposit to get a 1 year extension of an OA visa. You can use your home country bank deposits to get the original 1-2 year visa.
As an American I just sign it myself and send it back. I’ve got my proof of life letter waiting for me in Thailand. I will return tomorrow and sign it in the next week.
I would suggest using an agent to get a Thai bank account. The rest you can do yourself if you are patient, organized, and give yourself time to to make a mistake or two