I just enquired about the 800k thb deposit for a retirement extension and she was not interested in where it came from, just how long it was in my account. It was one day short of 2 months so she said I could still apply if I pay 500thb for a one day overstay...lol.
That applies only if u r withdrawing funds from your Thai bank with a Thai debit ATM card. But if u r using a foreign credit card there is always a Thai fee of 200+ thb.