The others were just in the wrong place at the wrong time.

'The hill-tribe people were being killed like pigs and dogs,' said Wiwat Tamee, head of the Highland People's Task Force, as he helped a relative of the dead fill out a request to reopen the case. The human rights worker recently returned to the hillside hamlet of Ban Pang Khon to help the National Human Rights Commission investigate one of the thousands of attacks carried out during deposed prime minister Thaksin Shinawatra's deadly 2003 operation, dubbed his war on drugs.

Now the post-coup government, headed by Prime Minister Surayud Chulanont, has launched a six-month probe to reinvestigate 40 of the unsolved murder cases originally completed by the rights commission, but ignored by the previous government.

The official death toll during the three-month campaign to eliminate amphetamine dealers is 2,598, but international rights groups estimate the toll to be twice that number.

The government policy, designed and implemented by Mr Thaksin, was simple. 'For those who are still selling drugs, the government has set two options for them, either it is prison or a temple cemetery,' he coldly said in a nationally televised speech.

And the results were swift.

'Normally there are only 250 murder cases in Thailand per month but during the first month of the war on drugs in February the murder rate was up to 800-900 cases,' said human rights lawyer Somchai Homlor, from the Lawyers Council of Thailand.

In fact, the last official government figures on the dead released on February 26 - before a ban was imposed to silence the critics - was 1,140. The government blamed the deaths on drug-related gangland violence, but human rights groups say the executions bear the hallmarks of police and military hit men.

'According to our investigation it is quite clear that the killings were committed by policemen,' said Mr Somchai. The 44-year-old lawyer is assisting the National Human Rights Commission of Thailand to form a working group to monitor cases assigned to the Department of Special Investigations by Mr Surayad this month.

'We will try to bring the mastermind of the crime, ex-prime minister Shinawatra, to trial because he is the one who really made the policy and instructed the officers to use tough measures against the suspects,' said Mr Somchai.

The policy guidelines that legal experts claim gave the 'green light' for extrajudicial killings were set up in a pragmatic, business-like fashion - a trademark of the tycoon-turned-prime minister's business executive style.

Financial bonuses and promotions were given to officers who filled the weekly quotas of arrests or deaths of the almost 50,000 suspected drug producers and traders on blacklists assembled by officials in the 76 provinces.

One government document included a sub-clause stating that the arresting officer was entitled to up to 40 per cent of the value of the drugs or assets seized even if the suspect died. State officials could pocket up to 40 per cent of the value of alleged dealers' assets seized after an arrest, leading to claims police were planting drugs on dead or alive suspects.

Widespread fear enveloped the nation as letters bearing a government stamp were sent out to suspects listed on the Kha ta don - death list - ordering them to turn themselves in and sign a paper vowing to sever their involvement with drugs or face drastic action.

Many were killed by gunmen shortly after leaving the police stations.

It is possible many officers felt they had no choice. Those who did not meet the weekly arrest quotas - from an order to 'reduce' by 25 per cent the number of people on the blacklist by February 25 - faced disciplinary action including dismissal or moves to inactive posts.

'Thaksin closely monitored and enforced the implementation of his policy, essentially giving police a licence to kill,' said a human rights commissioner, Vasant Panich, who accused police of trying to abduct him earlier this year.

Fellow human rights commissioner Pradit Chareonthaithawee received telephone death threats following criticism of the Thaksin policy at a special UN meeting in 2003.

Former senator and government critic Kraisak Choonhavan will head the working group and he has hailed the new government for its promise to investigate the cases. 'If this government wants to achieve political reforms, it must deal with Mr Thaksin,' he said at a recent human rights forum in Bangkok. 'No progressive constitution can usher in political reforms as long as Thai society allows a person linked to the murder of so many people to go free.'

While the former prime minister is at the centre of the investigation, the Asian Human Rights Commission's Nick Cheesman stresses the importance of bringing the individual killers to justice. 'I am sure that is a concern for the family members as well to find out who was responsible on that particular day for one of their family members being killed,' he said.

But it may be difficult to prosecute the gunmen in the country's top court as the police hold a level of impunity in Thai society, and are capable of using intimidation and fear to scare opponents. And for one daughter, the intimidation may have already started.

For Wassana Hemmun, the clearing of her dead mother Ooy's name is long overdue. The 48-year-old wife of a public health official was shot dead on April 22 in 2003 - one week before the end of the three-month campaign. Ooy was riding on her motorcycle to a district office in Phetchabun province to prove her part-time earnings as a loan agent were legal.

'My mother had been told by local police that her name had appeared on one of the blacklists and she feared for her life,' said Ms Wassana.

Since the case was reopened for investigation she has received anonymous phone calls from a man claiming to be an NGO worker requesting to see her mother's documents.

Human rights groups believe it may be the work of rogue police involved in the killings.

'People who come forward need to be given assurances that they won't be subjected to threats or other kinds of intimidation,' said Mr Cheesman, who is based in Hong Kong.

'But one thing to keep in mind, innocent or not innocent is not the issue, what we have to keep in mind is anyone that is accused of anything is entitled to be prosecuted by the due process of law. Under no circumstances are these killings acceptable.'

Still, all parties agree the reform must start with one conviction.

'If you look at the many cases and every case leads to the mastermind I would like to see what the court will say because all the evidence leads to one person,' said Mr Somchai.

But the self-exiled Mr Thaksin, now in Beijing, says he was not alone in the war on drugs and that Mr Surayud, who was then army chief, also co-operated in the campaign, Thai news agencies reported last Friday.

Meanwhile, demands are increasing to reopen more cases as awareness spreads among victims' families.

'There are about 6,000 hill-tribe villages in the two northern provinces and we have estimated at least two people from each village went missing or were killed,' said Mr Wiwat, as he files a new complaint from one of the villagers, using an ink blotter to fingerprint those who can't sign their names.

The location of the hill-tribe massacre was visited by a local shaman last year to rid the area of the bad spirits, but many villagers claim to still hear the victims at night. 'The spirits of the dead have not been treated justly. Their names must be cleared so that they can find a clear path to the next life,' says one mother, whose son had hitched a ride with the ill-fated truck to help her in a nearby fruit plantation.

Like thousands of other victims, the young man had no connection to the amphetamine trade, but was simply collateral damage in a systematic campaign whose policy condoned the elimination of suspects.