Before you make an NNID, go to your system settings. Select miscellaneous settings (bottom right), user profile, area. Set it to another region, for example US > Singapore, and you should be able access the Singapore shop instead of the US one. People did this to take advantage of the lower prices in some regions before NNIDs were implemented. I don't know how it works now since the implementation of NNIDs, but a message pops up saying you will be locked out of your account or similar, so I haven't tried it. You could make a emunand backup and see.