Ah, that sounds nasty Frank, I have to say that I have always been with Nationwide in the UK using their Flex Account, no withdrawal fees and the exchange rate is very similar to the local banks, the last withdrawal I made I got just over 46 and the official bank rate here was a tad under 47, so much easier to swallow.
As for the 150 baht ATM withdrawal fee, I do believe you can make a saving on this by using the AEON bank ATM in the Big Jieng (Tesco) complex

, where I think it is only 40 baht or thereabouts.