Yes, how well I remember those signs (also in Singapore) - I travel with medicinal opium (by prescription, for control of diarrhea). You can imagine how I felt going through customs in those two countries. Fortunately, I didn't get searched.

In fact, the only times I've ever been searched were from Amsterdam going into London, and then again a few days later returning to the US. The latter time I wasn't worried about the opium (I'm a citizen and it's a prescription; what could they do), but the Brits did find it: they waved a sort of dustbuster over my luggage and analyzed the filter. "Mr. Johna, it's testing positive for heroin or opium, do you want to tell us anything?!" They took the opium to check with a supervisor, and brought it back: "no problem".

I was just glad it got found in a friendly country where I speak the language!