In the global narcotics economy, drugs generally flow in one direction — from not-so-rich parts of the world toward wealthier countries, where more people can afford to get high. But strangely enough, contraband is now flowing the other way. The drug in question is US-grown cannabis. American criminals are smuggling it en masse to Thailand. Weed is legal in nearly two dozen US states, so what could justify trafficking pot 8,000 miles eastward across the ocean? The World’s Patrick Winn reports.