Get the non-O. Go open a bank account asap once you arrive. Might need to check what paperwork they want. If you have a Thai friend can go with you that helps. The point us with Non-O you'd need to deposit 800,000 tbt to get the one year extension. If that's the time you'd need. The non-OA doesn't need the money in thailand. So it may suit you. I'm so sorry to hear of your brother's death. What a terrible time for you.
there's no difficulties opening an account when on a non-O. The non-OA doesn't require a bank account but is linked in date to the insurance. Which can be costly and not very good.