The Cambodian black market trade of illicit drugs includes cannabis, methamphetamine, and high grade heroin. It is reported that foreigners requesting cocaine are sometimes provided with heroin instead

A few weeks ago an American working for one of the Phnom Penh English-language newspapers died of what is widely believed to have been a drug overdose. Another three of the newspaper’s employees also overdosed, but luckily survived. Each year at least a few foreigners are found dead in Phnom Penh guesthouses of an accidental overdose. The main reason? Buying cocaine that is actually heroin.
Cocaine in Cambodia is expensive — more expensive than heroin. Because heroin is produced in Southeast Asia, it’s cheap and far more pure than what’s available in the West. Often dealers in Phnom Penh will agree to sell cocaine but will actually deliver heroin — whether it’s due to stupidity or a gruesome cost-saving method is unknown. In 2009 this tragic trend made the headlines when David Hunt and Mark Ganley, two Britons on holiday in Cambodia, died after taking heroin that they thought was cocaine. Although this case is well known, many more die each year in cases that do not make the headlines.

Both expats and tourists meet untimely ends quite regularly in Cambodia, often under mysterious circumstances that involve drugs. Heroin is much cheaper in Cambodia than cocaine, so it is often used to cut cocaine or sold in its stead. So when abusers rack up a big line of what they think is cocaine, they may quickly find themselves unconscious. The unreliability of Cambodian information applies to drugs as much as to everything else. A tuk tuk driver will tell you he knows exactly where you are going and end up lost for an hour, so it’s unrealistic to expect this same tuk tuk driver to know the difference between various Class A substances.