Located on the left bank of the Chao Phya River, Thailand's capital, Krungthep, known as Bangkok to Westerners and "the City of Angels" to Thais, has been home to smugglers and adventurers since the late eighteenth century. During the 1970s, it became a modern Casablanca to a new generation of treasure seekers, from surfers looking to finance their endless summers to wide-eyed hippie true believers and lethal marauders left over from the Vietnam War.

Moving a shipment of Thai sticks from northeast Thailand farms to American consumers meant navigating one of the most complex smuggling...