At first the tablets made life easier for Santhisuk: they helped him endure the long hours lugging heavy fabric bales in a Bangkok textiles factory.
Gradually he noticed he was angrier and more aggressive on the days he skipped them. But it was only when arrested for a third time – and sent to rehabilitation at a Buddhist temple – that he admitted his addiction to methamphetamine.
Now clean, the 19-year-old labourer is worrying about what will happen when he leaves the sanctuary of Wat Saphan and returns home.
"It will be difficult because all my friends still take it. Drug use is so widespread now that everybody thinks it's normal," he said.
Monks at the temple in Klong Toey, one of Bangkok's poorest areas, say they have seen a huge increase in addiction rates. The problem has spread far beyond the Thai capital.
The number of methamphetamine users in Thailand will reach 1.1 million this year, the head of the country's anti-drug police told the Guardian - equivalent to one in every 60 citizens. The number of users has soared by 100,000 annually over the last five to six years, said Lieutenant-General Atitep Panjamanond.
Yingluck Shinawatra, the prime minister in waiting, has already pledged "a new war on drugs" to eliminate them within 12 months, alarming human rights groups who fear a repeat of her brother's 2003 crackdown.
More than 2,500 people died in three months after Thaksin Shinawatra ordered police to draw up blacklists of suspected dealers and act "decisively and without mercy". Though the police blamed gang crime for most of the deaths - they said 68 were shot by officers "in self-defence" - human rights groups say there is compelling evidence of extra-judicial killings. A committee later reported that more than half the dead, including a nine-year-old boy, had not been involved in the drugs trade.
But the campaign was hugely popular and as drug use rises, many want a return to tough action.
"Personally, I think the killings were a good thing. If you leave it to the courts [dealers] just cycle in and out of prison," said Aminna Bedinlae, 84, who lost her son to drugs and now runs anti-abuse programmes in Klong Toey, where 46 residents were shot.
Substance abuse had always been rife in the Bangkok slum, but in the past glue-sniffing was more common, said the 84-year-old. "Now they start off sniffing glue at six or seven and move on ... [Methamphetamine] is more expensive so they get involved with crime – theft or burglary– and it makes them more aggressive.
"My neighbour's son steals from the family and demands 300 baht [for drugs] every day. If she hasn't got it, he hits her." Drivers and labourers have long relied on methamphetamine tablets – known here as yaba or "crazy drug" – to sustain them through gruelling work sessions.
But Atitep said recreational use was extremely common and that children as young as 13 are taking it, with five- and six-year-olds being used as mules. Last month the public health minister said 6,700 children aged 7 to 17 were rehabilitated in the first half of this year.
Experts warn regular use can lead to addiction and psychiatric problems, and say the drug is associated with violent and aggressive behaviour. Atitep said about 70% of methamphetamine comes across the Burmese border and blamed ethnic militias for churning out more drugs to fund their fight against the regime.
The price of a tablet has fallen to as little as 150 baht (£3) in places; half the 2004 price. His department seized 33m tablets in 2009, and 60m last year.
"That doesn't give me pleasure, because there is a lot more supply," the police chief said. "Today we seize 1m tablets. Tomorrow they produce 2m."
One of his teams had just seized 30,000 tablets in Nakhon Pathom province. But officers who traced the gang bosses behind the deal discovered they were already jailed and had continued to trade via smuggled mobile phones.
Atitep said changes in values and society were contributing to increasing drug use. Others say the economic fall out from 2008's global downturn, and the distraction of authorities by political turmoil, have exacerbated problems. Some allege that corrupt officers are facilitating the trade.
At Wat Saphan, monks fear another crackdown would only push problems underground.
"When Thaksin came along it was brutal. There was shooting — bam, bam, bam – and were the results worth it?" asked one monk, Phra Kru Manit. "Do you know who the kingpins are? Do you know which officials are involved? Deal with that, then deal with the problem on the streets." The real solution lay in rehabilitation programmes and better educational and economic opportunities for residents, he argued.
Yingluck told AFP before the election that she would "handle the drugs policy with care [for] human rights".
Montira Kantapin, a spokeswoman for Yingluck's Puea Thai party, said a working group was considering options.
"No one is disputing the government's desire to take on the drugs industry. It is the means we are concerned about," said Benjamin Zawacki, Amnesty International's south-east Asia researcher.
Sunai Phasuk of fellow charity Human Rights Watch said Yingluck's pledge to eradicate drugs was the group's biggest concern.
The outgoing government had identified suspects in a similar way but "with the Democrats' approach they are sent to a bootcamp facility [without proper medical help to quit]; with Thaksin's approach they might end up dead," he said.
He said that many of those killed in the 2003 crackdown had been "victims of personal revenge or sloppy categorisation". One couple was shot dead after acquiring suspicious wealth; it later emerged that they had won the lottery.
Guardian 10th July 2011