The culture in Singapore is still quite conservative. Thus, I think most of the people are still not able to accept pumping openly. You can use nursing shawl or cover in public or pump privately in a nursing room, where most of the shopping centre has this facility. There is a device called freemie cup that you can use to pump your milk hands-freely, http://www.pupsikstudio.com/freemie-deluxe-collection-cup-set.html My friend uses it to pump at her workstation and in mrt, cover her pumping session with a nursing cover.
I pump in public, albeit under a shawl and when hubby is around. I am a little shy about it, but I boil it down to new mum nerves. :)