I went to 3 banks and asked because I am thinking of switching from Retirement to DTV. Bangkok, K and TSB. Here is what I was told.

1. You can't get a new bank account on a tourist Visa, unless you have property here (and/or a Pink Card), or are married to a Thai

2. Any Bank accounts already open, will not be closed just because you change to a tourist Visa, (Your history of time is evidence you are not a new account for illegal activities)

3. No effort is being made to investigate and close any accounts that do not look suspicious (many multi millions of baht transactions, new accounts not being used etc)

Hope that helps

Caveats:

1) If you are Russian or Chinese then you will face more issues as your countrymen are the majority of the high publicly for fraud that started all this.

2) If you got a Bank account on a tourist Visa before 6 months ago .. Things have changed your experience has no relationship to today situation