Staring out from behind the bars of the Bang Kwang prison, Dieter still has a look of innocence about him.
Not that he tries to deny his guilt. "They told me that I'd get $17,000 if I carried just two kilos [4.4 lbs.] of heroin through Bangkok," the young German explains as he smiles nervously. "I just built a small house and had been struggling with debts for a year. I needed fast money. They said, 'Go to Bangkok, pick up a piece of luggage, and come back.'
"They convinced me that there was no risk," recalls Diether (not his real name), who has served three years of a 50-year sentence for drug trafficking.
Probably betrayed by an informant in the organization that employed him, Dieter was one of the unfortunate ones. Each year, an unknown number of couriers slip through Asia's airports undetected. "Of all the cases I've seen, only about 1 percent were not arrested following a tip-off," explains a volunteer in Bangkok who helps drug addicts.
Thailand lets couriers like Dieter get off relatively lightly compared with other Asian nations. Typically, the death penalty is commuted to a life sentence or a 50-year jail term here. Most couriers spend up to eight years in a Thai jail before getting to transfer to a prison in their own country. In Malaysia and Singapore, the mandatory sentence for drug dealing is death.
But in the larger scheme of things, couriers are expendable foot soldiers in the service of cartels that must find willing, and credulous, human mules to transport illicit cargo to Europe or the United States.
The couriers, argue some, are the most innocent tip of a vast criminal iceberg. "It's unfair to make a blanket statement about these prisoners. There is a percentage of them who simply made a mistake, and they're paying dearly for it," says Marie Susan, a New Zealand-born charity worker who visits couriers in Bangkok's prisons.
In official circles, however, even drug couriers with a clean criminal record and a middle-class American background elicit little sympathy. "I think it's pure greed that motivates them," says one Western diplomat familiar with drug enforcement.
"When they leave home, most couriers know what they are doing," adds Richard Dickens of the United Nations Drug Control Program in Bangkok.
Another inmate at Bang Kwang prison, a Frenchman called Claude, says he spent months preparing his "mules" for their missions. "Sometimes, I'd use my contacts with the police to test them by setting up mock arrests. I'd tell them to just speak English and pretend they were innocent tourists.
"None of mine were ever arrested," says Claude proudly. Trawling the travelers' ghettos of Bangkok for recruits, he preyed on individuals he was sure he could control. "Time wasn't important. I'd work on 10 people at the same time for months. I'd show them that with me, there was no risk," he says.
While more than 1,600 foreigners were convicted on drug charges in Thailand in 1996, nobody can be sure just how many couriers get through. Claude estimates that couriers move through Bangkok's international airport every day.
"I reckon only about 5 percent of those who leave ever get caught," Dieter adds.
Drug-enforcement officers here hope that is an exaggeration but recognize the difficulty in detecting couriers. "We're catching around 20 percent of those going through," estimates one police source in Bangkok.
"If you're wearing a suit and are sitting in the first-class lounge, nobody's going to search you," says Mr. Dickens. "X-rays can detect suspicious compartments, but it usually comes down to advance information."
Confronted by these obstacles, much of the drug-enforcement war is being fought not in airports and ports but in the jungles where opium is grown.
Even so, the difficulty in penetrating the forest-covered mountains of Southeast Asia's notorious Golden Triangle continues to hamper control efforts. Despite a significant decline in opium cultivation in Thailand, the US State Department estimates that Burma (the world's largest opium exporter) continues to produce more than 2,000 metric tons a year.
For the recruiters and couriers who funnel Southeast Asian heroin to markets in the US, that means that business is likely to continue as usual. "It's an excellent way of spreading the risk," Dickens explains. "If you divide 100 kilos of heroin between 10 couriers and one is caught, you only lose 10 percent of your merchandise."