No, most offices will not accept any funds at all unless it's your salary from a Thai job. But in my reply I clearly state that if they accept transfers, it must be shown as an international transfer.
A visa does not guarantee your entry into Thailand. It just determines how many days you will receive when you are allowed in. You can theoretically get 9 months, but there are stories of people getting interrogated after leaving and returning the first time as they are not following the pattern of a tourist while using a tourist visa.
The very first thing you need to do is go to your immigration office and ask them if they will accept monthly transfers.
Many immigration officers will not accept this for marriage extensions. The only income they will accept for marriage extensions is proof of your wage from a work permitted job in Thailand being over 40,000 baht per month.
If your immigration does accept proof of monthly transfers, then when you apply for your extension you must be able to show that you received at least 40,000 baht as an international transfer into your bank account (in your name only) every single month for the previous 12 months. If you miss a month by even a day, you will not receive your extension.
A METV does not give you 3x30. It gives you 60 days each time you enter, an unlimited numbers of times before the expiration date. Each entry is eligible for one 30 day extension.
Bank staff don't know anything about immigration. OX visa is simply not used.
In order to open a bank account they just need to be on a long-term visa or extension. Even a non-O visa suffices, and it's only 90 days. Those 90 days are meant for opening the bank account you must have in order to get the 1-year extension.
But each bank branch manager sets their requirements for that bank branch. There are many that simply won't deal with foreigners so they will make rules that are impossible. Just go to the next bank branch down the street and try there. Eventually you'll find one that will open a bank account with a long-term visa and a residence certificate from immigration.
Don't even bother trying if he's in Thailand as a tourist, as banks no longer open accounts for tourists.