That is a question you should be asking your school. Your school needs to develop some paperwork to allow your husband to get a Non-O Visa Based on Being a Trailing Spouse.
I heard there are a LOT of issues with people who have under-the-table volunteer visas, leaving Thailand, and returning for a tourist visa. I've seen people get rejected on entry, or get grilled hard at passport control.
IF you want to be safe, I highly recommend leaving Thailand, getting a new passport, and returning on the new passport.
That's a small-ish island. If you attempted to open a bank account at all the banks there, you may have to go to the mainland, OR go to Phuket.
If one bank branch rejects an application to open an account, visit another bank branch. Most bank branches operate in shopping malls or department stores. Opening a regular savings account should not cost more than 1,000 THB for a minimum opening deposit, however other accounts may have different opening requirements. There are over 6,000 bank branches in Thailand, and there will be a bank that is willing to open an account. A bank at Central Festival in Phuket should allow a person to open an account easily.
I shouldn't have to say it, but foreigner attempting to open a bank account should dress modestly. Males should wear closed covered shoes, long, respectful pants that covers the knees, a shirt that covers the shoulders and does not show the stomach, and is respectful design. Females should wear closed covered shoes, either long pants or a modest skirt but not yoga pants, and a top that covers the shoulders and midriff. Sandals, swimming shorts, or tops that do not cover the shoulders should not be worn inside a bank. I also recommend letting them know you'll deposit the 800K THB in the bank as soon as the account is open.