"The longer I can stay awake, the longer I can drive, and the more I can earn," he says. "I don't think I could do this job without my tablets."For hundreds of thousands of other low-paid, overworked Thais, amphetamines are seen as an easy way to boost personal earning power in a nation obsessed with materialism.
Known as yaa baa (mad medicine), amphetamine tablets are bought by the Thai poor as a means, not of recreation as in Europe and America, but of boosting energy to work harder and longer. Typically, it is taxi drivers, long-distance truckers, and factory workers, all paid by the hour, who are dependent on yaa baa. The more they swallow, the more they earn.
"There is a definite link in this part of Asia between amphetamine use and economic development," says Richard Dickens of the United Nations' International Drug Control Programme in Bangkok.
"We have watched amphetamines and other stimulants surge in popularity in virtually all of the dynamic 'tiger' economies of east Asia, starting with Japan after the Second World War, through South Korea a decade ago," he added. Thailand's problem with stimulant abuse, now reaching epidemic proportions, according to the UN, first came to the notice of the authorities in the early 1990s: at the height, in other words, of the country's boom years.
"This is a regional problem. We are increasingly concerned about the spread of amphetamines into China as well. With the Chinese economy now expanding so rapidly, and the pressure that is putting on working Chinese, there is potential for explosive growth," warns Mr Dickens. That possibility has not escaped the region's drug producers, aware that in the long term, amphetamine production offers more secure, and even bigger profits that the area's traditional drug product - opium.
Deep in the jungles of the notorious Golden Triangle region of Thailand, Burma and Laos, new factory-laboratories are springing up, mass-producing amphetamines to meet a seemingly inexorable rise in demand.
Anti-narcotics police say the producers are headed by the same secretive and heavily-armed drug barons who monopolise opium growing and heroin production in the area. Their intelligence reports even suggest a complete change of production in some areas from opium to amphetamines.
In many ways, manufacturing amphetamine tablets is much easier than heroin production, which requires large quantities of raw opium.
Amphetamine tablets can be produced in their millions, with relatively small amounts of either synthetic or naturally occurring ingredients mixed in small, highly-mobile laboratories less vulnerable to detection than the vast poppy fields that encumber the opium producer.
The other crucial factor is that, whereas heroin's overseas market requires complex international trafficking networks, stimulants like yaa baa are sold and consumed by locals, or, at least, by people a short truck or boat ride away. That, say police, means producers get an almost instant profit on their drugs. Tablets which cost as little as 6p to manufacture can fetch up to pounds 3 on the streets of Bangkok.
At night, "long-tailed" speedboats thunder along the city's klongs, a complex network of dark, narrow and polluted canals which connect disparate city districts, delivering literally boat-loads of tablets to freelance dealers who each buy small amounts to sell at taxi ranks, petrol stations, even Buddhist temples.
But there is also a new and growing market for yaa baa: schoolchildren. Under increasing pressure to perform at schools from parents and teachers, children as young as 10 are becoming dependent on the drug as a means of staying awake to study harder and longer. "It started as an experiment, to do what my friends were doing" says Chiraporn, a 15-year-old schoolgirl. Her three-year amphetamine habit was discovered by her father after she complained of anxiety attacks, nightmares and sickness. An investigation revealed that 40 per cent of her classmates were regular yaa baa users.
This rapid penetration of amphetamines into the respectable world of the Thai middle classes has jolted the authorities into tackling a drug traditionally confined to the country's impoverished.
Posters warning of the dangers of dependency have been stuck on walls and lamp posts, and police have been targeting peddlers. But despite more than 50,000 arrests last year, demand for yaa baa is growing. And the country once notorious for its number of heroin and opium addicts now has more than 300,000 amphetamine users, according to official figures - more than any other nation.