This is one of those "pot luck" questions! It's really dependent on who you get and what the bank manager had for breakfast that morning! I've opened 2 bangkok bank accounts - both whilst on 30 day visa exempt stamps. My Thai partner was there to explain that I was opening the account in advance of moving there. On both occasions, it took a while, but I left on the day with my visa debit card and my passbook. Keep trying!