When approved, the "visa" is the permission to enter within 90 days. On entry you receive 60 day stay as a tourist. You can extend that by 30 days. Keep trying other banks. . Foot slog!
because he maybe thought the "visa valid for 90 days" was how long he could stay. But it's not. It's valid for 90 days to use for entering the country.
don't know what site thats from. Looks like that's for people who aren't entitled to enter without a visa. You don't say what passport you have. UK passport holders can enter Thailand with no visa for up to 60 days. And you'll be in transit and not entering Thailand anyway.