One thing that strikes everyone, I think, who visits Singapore is the apparent racial harmony. Here is (to British eyes) an example of a multicultural society functioning perfectly, people expressing their religious and national peculiarities within the scope of a shared identity in a sense indistinguishable from that expression itself. Or, to more integration-minded visitors, perhaps an example of multiple and potentially hostile communities being successfully moulded into a united republic. Not laicité, perhaps, but certainly integration.
The problem comes, though, if you zoom in a little more. Perhaps the distinctive feature of the urban landscape isn't integration, it's separateness, different communities measuring out their different districts. That is, after all, how the tourist knows they are in one of the most diverse cities in the world. This is a challenge for the multiculturalist, because this version of it is very different to Britain's.
In the UK, the (begins to sound like a junior minister) Challenge of Diversity was handled essentially by laissez faire methods. The key virtue was tolerance, and the key sin racism. The principle was essentially that if other people were different, then this was none of your business so long as they kept their nose out of yours. This is not a bad minimum, after all - George Orwell wrote that one of the guarantees for democracy in Britain was that Nosey Parker was one of the worst insults you can throw at someone. But the downside is that, as Soizick says, tolerance is not far from indifference.
By the way, there is nothing wrong with using the word tolerance here - yes, you tolerate something bad, but tolerance is also defined as the permissible deviation from a norm. Toleration has often been used in a positive sense historically.
Getting back to the point, if it slips to just being indifferent to other people, you end up with a dangerously alienated society. This was pretty much what the Cantle report said was to blame for the 2001 Bradford riot, by the way. The French call this communautairisme, which might be better translated as communalism. Closed communities live out parallel lives without touching in a degraded public space.
Singapore's take on multiculturalism is much more dirigiste and integrationist, making constant efforts to build an (artificial) national identity around the cultures, charging bloggers with sedition for saying rude things about Malays. But the result is the same; communities of identity appear. Society functions, though, even if the Chinese, Malays and Indians would prefer to socialise in-group and the expats hang out in their own depressing flocks downtown. (A semiotics lesson: outside a bar full of only white people, an advert for that bar. On the advert, a cartoon couple. The woman is dark-haired and evidently Chinese. The man looks much the same except he has a line of red hair. What message is being conveyed? And, for bonus points, where are we drinking?)
The lesson, then: multiculturalism is possible but communatarianism is inevitable.