People have written to themselves as employees from themselves as Directors of the company authorising remote work from Thailand. The company stamp, seal or "Chop" is pretty much an Asian thing these days.
For the DTV I have not seen any posts where anyone was asked to show proof of the 500k upon entry or re-entry.. The only time anyone has been asked to prove they still have the 500k after approval is for an in-country extension.
RadiantButterfly205 Then as other have said go to local Revenue Department and ask for a TIN. 180 days plus assessable income and they will give you a TIN