You might want to consider using an agent to get the 800,000 into you Thai account and not bother with a marriage visa ,you can leave the money in your home country earning interest in a investment account and the interest will more than pay the agents fees every year.
no need for an agent to help you will bank account you have a non O visa ,get a certificate of residence from you local immigration office then go to the bank to open an account a.s.a.p,do not use Bangkok bank I have changed to Kasikornbank much better customer service and easy to open an account.
I Thailand Qr codes are used to scan to pay for almost everything, there is an app that can be used to allow to link you own bank account from any country and pay using your phone to scan a qr code it is very easy and simple to use. TAGTHAI is the name of the app even street vendors use qr scans.
Times have moved on this is extremely difficult and expensive to do now it is better to apply for a non O visa in your own country then using the Non omO visa open a bank account in Thailand when you arrive,you can then get an agent to deposit the money in your account to get the extension. Use Kasikornbank as this is the best at the moment for doing this ,do not open an account in the Bangkok bank because you will have trouble.
Things have changed since the crackdown on bank accounts ,you need a bank accounts now to get the Non O visa.
If you apply for a non O visa in your own country arriving in Thailan you can use it to get a bank account you can then extend the Non O.
I have been told by a popular agent in Pattaya they can't open bank accounts anymore,other people have said there are agent that can still open bank accounts at a cost.