JIM MIDDLETON, PRESENTER: Criminal syndicates in Thailand are rounding up thousands of pet dogs and strays to feed the illegal dog meat trade.
Dog meat is eaten by people in parts of Vietnam and China, and criminals are using Thailand as a hunting ground.
That's upset animal rights campaigners, who are fighting back.
And a warning - many viewers may find the pictures distressing.
Iskhandar Razak reports.
(Footage of dogs in cages is shown)
ISHKANDAR RAZAK, REPORTER: It may not look like it but these dogs are the lucky ones. They were all bound for a slaughterhouse in Vietnam or China but the operation to send them there was busted by Thai authorities as part of a growing battle to stop the illegal dog meat trade. In Thailand the trade is outlawed. While in other parts of the region itís acceptable and entirely legal.
JOHN DALLEY, SOI DOG FOUNDATION: I liken it to a war almost. Itís not won yet but we're certainly on the offensive.
DR BURIN SORRASITTSUKSAKUL, THAILAND LIVESTOCK: (translation): We have police out patrolling the border area. We do not support the trade. We're trying to control the border area by setting up special teams to work with border military and border police.
(Footage of men on truck taking dogs courtesy of Wildlife Friends Foundation Thailand is shown)
ISHKANDAR RAZAK: There's an abundance of dogs in Thailand. For years gangs have been roaming the country's north rounding them up. Sometimes they're bought from poor villagers, but many are taken from the streets or stolen from homes.
VERNA SIMPSON, HUMANE SOCIETY INTERNATIONAL: That can't be done as a single operation. We're talking about gangs who are lifting dogs, getting them to boats and the boat keepers and so it is, yes, itís a whole cartels.
(Footage of dogs being force-fed is shown)
ISHKANDAR RAZAK: After the dogs are taken, they're force fed to increase their weight so they can be sold at a higher price. Some suffocate and die in the process.
Those that survive are shipped in overcrowded cables across the Mekong from Thailand or Vietnam or China where it is legal to kill and eat dogs.
(Footage of dogs in cages on boats is shown)
Many are injured by the journey.
At the slaughterhouse the dogs are killed in front of each other in basic conditions. With that vision is too distressing to show here.
GILL DALLEY, SOI DOG FOUNDATION: I've seen a dog with no skin on it, a puppy, trying to crawl its way out of a boiling pot.
(Footage of women preparing dog meat)
ISHKANDAR RAZAK: Some in Asia believe dog meat is a delicacy and has magical properties that increase virility and health. The skins are also sold for clothing or bags.
(Footage of dog hide being prepared)
JOHN DALLEY: We understand there is a trade in exporting dog skin, particularly to Japan, for the manufacture of golf gloves.
ISHKANDAR RAZAK: Originally the gangs operated without any police intervention making millions by selling dog meat to the wealthy.
But that is changing, thanks to groups like the Phuket-based Soi Dog Foundation.
The group says it has embedded agents in the north and along the border to try and catch the gangs at work and help Thai authorities.
GILL DALLEY: They've actually put their own lives on the line while they're investigating and spying on these dog traders.
ISHKANDAR RAZAK: Soi Dogs was originally formed by expats John and Jill Dalley to sterilise dogs and cats. The organisation has many local volunteers and is funded by overseas donations.
It was through this work that it came across the illegal dog meat trade and decided to join the growing number of animal rights groups in Thailand trying to stop it.
They say their work isn't about western ideals, but universal ones.
JOHN DALLEY: All the countries in South East Asia are trying to eliminate rabies, in fact they've all signed up to an agreement to eliminate rabies by 2020.
By transporting these dogs, which is totally illegal, to Vietnam - they're not vaccinated dogs, they in effect are compromising this.
ISHKANDAR RAZAK: In the past three months authorities from the livestock department say they've made several big busts and saved, spade and vaccinated thousands of dogs.
DR BURIN SORRASITTSUKSAKUL (translation): There was one arrest in January, twice in February, three times in March, four times in April and recently in May two weeks ago.
ISHKANDAR RAZAK: Those caught can face up to two years in jail for breaking the Epidemic Act and a fine of $1.60 US for each dog they have for breaking the Rabies Act. But when one kilogram of dog meat sells for three times the value of pork, they admit itís an uphill battle.
DR BURIN SORRASITTSUKSAKUL (translation): There are dog consumers there in China and Vietnam and when there's high demand they'll buy sources to full bill that demand.
ISHKANDAR RAZAK: Gill Dalley lost her legs to infection after saving a dog from a swamp years ago. Rather than give up, she says the loss inspires her to keep helping vulnerable animals.
GILL DALLEY: I can honestly say it is the hardest thing I've ever had to do. But it was the animals that spurred me on. I couldn't let them down. I just had to carry on helping them.
ISHKANDAR RAZAK: And with a growing number of local volunteers at the shelter and in the field, she isn't alone.
VERNA SIMPSON: We have generational change coming in over there that is making an enormous difference. The locals are actually the ones breaking the chains. They're following the trucks, breaking open the doors, releasing the dogs, and they're being very, very proactive, because itís their pets that have been stolen.