Manila: The Philippines president's order to shoot on sight those drug suspects who refuse to surrender never frightened 34-year-old Ramson Donado, who began running street errands for pushers when he was nine and has been addicted to shabu, a poor quality form of methamphetamine, for years.

"I have never been afraid to die … life is cheap here," he says.

But Donado says the white odourless substance he heated on foil and smoked seeking a rush of euphoria became expensive and hard to find after the bodies starting piling up across the nation in July.

In late August, the last time he tried to buy the drug in the narrow alleyways near Manila's sprawling Tondo slum, he was duped.

"It turned out to be candy. I thought then that maybe it's time to try to quit," he says.

Donado is one of more than 700,000 Filipinos who have surrendered to police under President Rodrigo Duterte's controversial war on drugs.

On Wednesday mornings he checks his name off with police sitting behind a desk in Manila's San Roque Catholic church and joins other addicts who put signs with their names around their necks, pledge never again to take illegal drugs, line up for a meal, dance to the Birdie Song and listen to nuns speaking about the evils of their past ways.

If they turn up for another nine sessions, police say they will be removed from a list of suspects who have been the targets of Duterte's campaign, which has left more than 3600 people dead since July 1.  

However parish priest Tony Navarrete says when he looks into the eyes of those who have surrendered he is not convinced they have reformed.

"We are doing what we can to rehabilitate them," he says. "We are hoping against hope that they will not return to their past ways."

Roberto "Bobby" de la Cruz, a former drug addict-turned-priest who runs the church's program, says the number of people who have surrendered has overwhelmed the country's jails and few drug rehabilitation centres.

"It's scary and disturbing. How can the country cope? The church is trying to do what it can because this is an issue of morality, but we too are overwhelmed," he says.

The chiefs of the country's districts and villages, called barangays, estimate drug use has dropped as much as 90 per cent since the crackdown began, although Fairfax Media has witnessed deals still being done on Manila's streets in the middle of the day.

Bong Parce, the 46-year-old chief of 65,000 residents in Tondo, says he is 100 per cent behind the crackdown despite killings by unidentified assailants who roam the area on motorbikes.

"I only ask the president: What is next? Where are the follow-up rehabilitation programs?"

The brutality and impact of the crackdown is unprecedented in the Philippines, a country of 100 million people where, according to official estimates, seven million people were previously addicted to shabu.

An opinion poll released last Friday showed that a majority of Filipinos rated the crackdown as "excellent", though there appears to be growing unease about suspects being killed instead of arrested.

But critics point to the failure of a similar bloody crackdown in Thailand in 2003 under then prime minister Thaksin Shinawatra.

An estimated 2800 suspects were killed in three months, only half of whom were later found to have had anything to do with drugs. Many of the victims were rivals of corrupt police. Prices of illegal drugs soared, but before long drug use was back to the levels seen before the bloodletting.

More than a decade later, an influential group of Thai officials, social advocates and academics are arguing the war on drugs has been lost and it is time to consider decriminalising methamphetamine and introducing more humane people-centred drug policies.

"The world has lost the war on drugs, not only in Thailand," Paiboon Koomchaya, an army general who is justice minister, said in July.

"Why do 70 per cent of drugs offenders remain in prison? Why does the problem persist despite thousands of deaths? And why do people still complain about drugs in their communities?"

 In the early 1980s the Indonesian leader Suharto presided over the mysterious deaths of up to 10,000 petty criminals in the capital Jakarta – many of them supposedly drug dealers.

The illegal drugs trade in Indonesia has boomed over the decades since while, as in Thailand, no one has ever been prosecuted over the mass killings.