it's not against the law to take photos of pple without them
knowing, but one would do well to observe privacy laws.
technically, the only places u are not allowed to take photos is
where they have a "no photography allowed" sign, and even then,
it's put there by the management. in other words they can ask u to
leave but they cannot charge u in court.
of course, there's many grey areas.
one local photographer complained that the security guard chased
him away while he was taking the fullerton hotel saying that becos
of terrorism, they don't want the place photographed. at another
time, some tourists (angmoh) were taking photos there and nothing
happened to them.
wat? did i hear u mention law?