Don't they like beaches and stuff? I know Sentosa sounds lame but that's about the only thing we have here, no? East Coast (aka most disgusting non-beach in Singapore, JB and some say Batam) notwithstanding..
Good thread, this.
I'd say either clubbing (Clark Quay to see local-versioned farangs trying to behave like they're in Sukhumvit), Sentosa or parks (don't think dirty). Movies are out because they don't have Thai subtitles (and Thai films on our screens now probably already bootlegged to death back in Thailand so it doesn't make any sense bringing them to see something everyone's watched 20 times back home).
Singapore
is a depressing country.