I went to 3 banks and asked. 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 (my situation)
3) No effort is being made to investigate and close any accounts that do not look suspicious (many multi millions of baht transactions)
Hope that helps