These bats were unlabelled in the walk-through aviary named "Malaysian Lowland Forest".
At the time I put them down as Cave Nectar Bats (Eonycteris spelaea) because I couldn't think what else they might be. They were in a somewhat-darkened crevice so I couldn't see them properly with the naked eye or on my camera screen.
However, looking at the photos on my computer they look more like one of the Rousettus bats. The most likely native species are either Geoffroy's Fruit Bat (R. amplexicaudatus) or Leschenault's Fruit Bat (R. leschenaultii). The Egyptian Fruit Bat (R. aegyptiacus) is also kept in some zoos in southeast Asia I think, but is less likely as a candidate.
I'm not sure any can be identified from photos though.
(Just as an additional note, the field guide for southeast Asian mammals says that the Cave Nectar Bat can be distinguished from the other species because it lacks a claw on the second digit - unfortunately none of the photographed bats show the wing properly).
