Well, my plan did not meet with great success. As I thought I recalled from Chiang Mai yesterday evening, K-bank's maximum withdrawal amount on offer was 10,000 baht. I tried 20,000, but it was an "invalid amount." Same results at Bangkok Bank today. (Last night, TMB and Bank of Ayudhyah offered 20,000-baht withdrawals.) I spotted a Standard Chartered across Charoen Krung from the Bangkok Bank branch I tried, so I decided to give it a go. The Standard Chartered ATM offered "fast cash" at the 20,000, but that was rejected as over my limit. Probably a Wachovia or a me issue, but that's what happened. Then I tried 10,000 baht, to test whether it would charge the fee. 10,000 worked, and there was no announcement of a fee. Receipt shows 10,000 baht withdrawal.
Assuming the fee isn't hidden somewhere, it appears that Standard Chartered is among those not currently charging the fee. Standard Chartered does not have a huge retail presence in Thailand-- far less than in Singapore or Hong Hong, and far less than Singapore-based UOB, which is building a retail presence here--but there are Standard Chartered branches and ATM's here and there. The one I stumbled across is on Thanon Charoen Krung (New Road) just at the foot of the Saphan Thaksin BTS Station, so it's more or less convenient to most of the Riverside hotels.