Not sure how much time you have, but I would *highly* recommend a Schwab checking account if you frequently travel abroad. No foreign transaction fees at any ATM anywhere in the world. It is, in all honesty, the most valuable piece of travel gear I have. Can get local currency out of any ATM anywhere and be good to go without needing to exchange cash or pay any fees. No minimum balance helps as well, I just store a few hundred USD in there for emergency use stateside and then transfer over however much I might need before an international trip. Have used it dozens and dozens of times in Singapore, never once had an issue.

If you don't have enough time to open an account or it doesn't interest you, figure out which of your cards has the smallest foreign transaction fee and go with that. Maybe pick the lowest two cards to be safe. Finding an ATM in SIngapore is not difficult. In my experience, every major hotel has one and you can usually find ATMs in any mall or shopping area.