Drugs factories flourish on the Thailand-Burma border
Its chemical name is methamphetamine, but in Thailand it's simply known as ya baa or "mad medicine".
Thais are estimated to consume 800 million tablets of the drug each year - the equivalent of 12 for every man, woman and child.
Sandro Calvani, head of the UN International Drug Control Programme in Thailand, says that ya baa is now threatening the very fabric of society.
He says the drug is so common in Bangkok that taxi drivers will sometimes give it as change if they don't have coins to hand.
Huge market
"I think methamphetamines are now the main problem for Thailand and the region," he said. "This drug delivers immediately, it's extremely cheap and easily available, and that is why it has such a huge market."
One man who sees the effects at first hand is Father Joe, an American Catholic priest who helps the disadvantaged in Bangkok's poorest districts.
His Human Development Foundation provides schooling for those who could not normally afford it and cares for Thais suffering from Aids.
Many of those he sees have been hooked on ya baa. He says that while methamphetamines may not have the notoriety of other drugs, they are highly addictive and cause mood swings which often result in violence.
Father Joe's views on the subject are clear. "It's the greatest enemy Thailand has ever had, and no one seems to want to do anything about it. Everyone's making too much money," he said.
Making ya baa
The manufacture of methamphetamines is thought to be concentrated in Burma, along its border with Thailand.
The biggest producer is believed to be the self-styled United Wa State Army, an armed ethnic minority group which can call on 15,000 soldiers. The drugs are then smuggled across the Thai border.
The trade has caused tensions between Thailand and Burma, which the Thai prime minister Thaksin Shinawatra tried to address in an official visit to Rangoon in June.
The United States has also agreed to send Black Hawk helicopters to the north of Thailand to help clamp down on the smuggling routes.
But use of the drug is so widespread that the authorities face an uphill battle.
With each tablet retailing at around $1, it is cheap to buy. It is even cheaper to produce, as - unlike heroin or marijuana - it needs no crop, just a simple laboratory.
One report by the Thai army estimated there are more than 80 factories in Burma turning out the drug.
Ya baa tablets are also small and easy to hide, which makes them ideal for smuggling. The trade is estimated to be worth well over half a billion dollars a year.
Father Joe is convinced the solution lies not in Burma but with the Thais themselves.
"It's easy to blame someone else for a problem you don't know what to do about," he said.
"No one has come out and said it might be morally wrong to sell them to our kids. The solution is with the parents and the communities."