wait till they check. You will be locked out. I have 4 accounts here 1 was frozen and the others were fine. It just depends on when they random kyc pops up. Which it will
They won't take your money. But they will freeze your account if they find out. The banks are more integrated now. They know when you get a new passport. Your bank account should be updated within 30 days of receiving your new passport
You are still required to pay taxes in Thailand if you work for a Thai company. They will with-hold your taxes on each pay check. Sometime in late January or early February they will give you a tax form for the year. You will take this to any revenue department and they will figure your actual tax amount. You may get a small refund, or you may owe money. There is no way of knowing this till you go. Amd taxes have to be filled every year to renew your work permit.
If you are switching from another visa or extention of stay to a retirement extention of stay it must be in a Thai bank. If you are applying for a 90 Non-O visa in the US it depends on the embassy. Some ask for proof of money, some don't