another addition on top + 'happy' cake
Sightseeing in Northern Laos picture - Note the sign that says "happy birthday cake". Any dink or food that has "happy' in it is laced with marijuana, or magic mushrooms, or opium or yaba (methamphetamine). This is a backpacker town, & this is common in most backpacker towns in the world. Although these drugs are freely available & advertised in Vang Vieng, they are all illegal, which explains the large police presence. Plain clothes policemen frequently take unsuspecting tourists to the local police station for smoking a joint. The usual outcome of this involves having your passport seized until you cough up a hefty "fine", typically between 3-5 million Kip (US$350-$500). Once the fine is paid however the matter is generally taken no further and the passport returned. The punishment, however, will depend on the officer you are dealing with.