I have an account with Bangkok Bank. Just not that well up with this modern technology. May I need to speak to them and try to get sorted. Maybe easier than keep going to ATM and carrying lots of cash.
From what I've seen the common way to make payments is from your thai bank account with a qr code. Don't know if foreigners are allowed to do this or not.
If you have the 800,000 just do it yourself at a cost of 1900 baht. I can understand using an agent if you don't want to keep the large sum tied up. But otherwise like I say just do it yourself.
I've not asked directly. I am just reading off the handout. I suppose for what it costs I just as well copy all pages and if not needed then no great loss.