Not in KL any more, but we‘ve never had problems with alcohol stored ON the aircraft.. It‘s when we stored it in the hangar that we had it confiscated, because there was no duty paid on it in Malaysia. When we asked about a legal way to store alcohol airside, the local uniforms were gloriously incapable of even suggesting how to go about it.
In short, if you can‘t keep it on the airplane because it will spoil, you‘re screwed... Because of the camera system installed in Subang, the usual 500RM bribe won‘t guarantee success...