who did not want van tuong to land in australia?

it was reported that nguyen van tuong was a transit passenger on his way to australia. passengers in the singapore transit lounge are normally left on their own. no checkings required. no custom officers are around parading the transit lounge except manning the entry/exit point. now how would the singapore customs know that a certain passenger bound for australia is strapped with heroin? obviously someone must have tipped off the singapore customs. van tuong is an unknown entity to the singapore customs. who would have known of him and his mission? who would have interest to want to prevent him from entering australia with his poison? our customs are not supermen who have laser beam eyes that can see through van tuong's jacket. neither were custom dogs running around the transit lounge. his arrest is no coincidence. would the australian media and public want an explanation? want to know who did it? now who tell? who told on nguyen van tuong?