the issue could be that they don't come in as international and so wouldn't be accepted by immigration. AFAIK GSB isn't a direct Wise partner so they will *never* come in as international there. You can get documentation from the bank they come through in this case but that might have been what they were trying to explain.
both of them could live in Farangland and be coming to Thailand to visit family or a holiday. Now in this guy's specific case maybe he's not entirely a tourist but Thai wife doesn't necessarily make you not a tourist if you don't live here.
it is normal, it's where they put you until you can get a flight out. If you are denied entry at an airport, there's nowhere else you can go other than immigration detention, until the flight out.
I got my DTV from London and I didn't have 500k for three months, only at the end. As did many others in this thread, and countless other threads on what London requires. I haven't seen anything suggesting they need the 500k there for three months.
They want the three months to corroborate your claimed income, it should show the money coming in corresponding with invoices/payslips.
they will take a utility bill or driving license. I gave them a utility bill. The statements have two purposes- showing you have the 500k at the end, but also showing your income over the period. This latter bit is what they want the three months for. I submitted invoices and then highlighted the corresponding amounts paid in in the statements. I only had 500k at the end, not for the full three months.
that means they want statements for three months. The money doesn't have to be there for three months, which is what OP was asking. So it's actually the opposite of what you are suggesting. Also "e.g." means "for example" - these are examples of what is required. You don't need a sponsor letter if you have the bank statements.
people seem to think there's a hidden field that shows it. But why would some consulates put it in remarks as well if there was a hidden field. I don't think they know from what they have in front of them.