Outside of the UOB ATM, I haven't seen any DCC prompts in Singapore, including the preauth on my World of Hyatt Visa at the Andaz. Most of my credit card transactions have been contactless, which may be bypassing DCC still.

The UOB ATM quoted 93.48 USD for 120 SGD. The Visa rate was 90.32 USD, so this was the 3.5% that the ATM quoted. Usually the quoted % does not match the Visa or MC rate. The screen even had language about understanding the costs of currency conversion. I would say this is probably the most compliant implementation of DCC that I've ever seen. (I'm still not a fan of course.)