Just because you are a sole proprietor surely the money isn't considered personal and you have rules as to what expenditure is company related as otherwise no one would ever pay tax would they? Surely you cannot expect visa officials to be accountants too.
I have a Thai account but I am finding it much easier to withdraw 20k baht from an ATM from my UK account. It also helps with the tax avoidance. No idea why people seem so obsessed with getting a Thai account. It cost me £465 today all fees inc.