Found this picture of the Creatures of the Night show in Singapore Night Safari, taken in October 2006; the extremely large tail to body ratio makes me think of a tree-kangaroo, and the black face and small size makes me think of Lumholtz's.
However, I can't find anything about any Singaporean zoo ever keeping this species, or the species ever leaving Australia at all.
I'm pretty sure it's not a tree kangaroo, but I'm not sure what it is. If that is the tail and not a leash of some sort or an effect of the photo, then it is an extraordinarily long tail though.
My bet would be on some sort of large rodent, perhaps a squirrel.
I think it's actually a small-toothed palm civet. I had a google for civets at the show there and found a video showing exactly what is happening in your photo (with the kid holding out his hands, in one of which is a grape).
