You'd be in a much better position to argue your point if you can get an LTR remote worker visa. It's much harder to qualify though, but if you do, that one makes you tax exempt completely for overseas income.
It has nothing to do with how long the DTV lets you stay. The DTV is specifically called a tourist visa in the law that created it, and the banks are not giving or keeping accounts for tourists.
IMMIGRATION will not let you pass without a TDAC. So it doesn't matter what government agency requests the information, it is REQUIRED BY IMMIGRATION to enter Thailand.
It's only Mandatory if you start filling that section out. If you start, click the "clear" button next to the air, land or sea selection and it will go back to not mandatory.
Get yourself situated. The bank will want an address and may even ask to see your lease.
That being said, you only have 30 days to get your bank account opened and get your money transferred. That's because in order to apply for the extension, your money must be in the account for 2 full months already. That means you only have 30 days to get that done or it won't be in your account long enough