I already have a Thai bank account with the 800,000 Baht deposited for over 2 months. I just needed a letter from the bank to immigration and a bank statement. I opened a Thai bank account several years ago. It seems that the rules have tightened since. I tried a couple of different banks in Chiang Mai recently. They wanted a copy of a work permit or non-O visa. Chicken and egg situation - can't open an account without a visa - can't get a visa without a bank account. Anyway, I think you need to plan a lot longer than a few weeks ahead. The experts may have better information or ideas.