Disturbing video footage of a bloody rhino hunt on a North West game farm raises questions about the National Prosecuting Authority's controversial decision this week to withdraw criminal charges against game farmer Marnus Steyl and a Thai national, Punpitak Chunchom.

Filmed in January last year, the footage – a copy of which has been obtained by the Mail & Guardian – forms part of a devastating digital trail of evidence that leads from South Africa to Southeast Asia. It shows Steyl, accompanied by a professional hunter, Harry Claassens, repeatedly shooting a rhino in what appears to have been an illegal "pseudo hunt", carried out at the behest of an international wildlife-trafficking syndicate.

This week, a key "lieutenant" in the so-called Xaysavang syndicate, Chumlong Lemtongthai, pleaded guilty in the Kempton Park Regional Court to 52 of the 79 charges he was facing, including numerous counts of fraud, customs and excise violations, and transgressions of environmental and organised crime legislation. He was expected to be sentenced on Friday. Lemtongthai is the most senior figure in a rhino horn-smuggling ring ever convicted in South Africa.

Charges against Steyl, Chunchom, alleged syndicate middleman Tool Sriton and two of Steyl's farm labourers, Patruis Matthuys and Obene Kobea, were abruptly withdrawn by prosecutor Allen Simpson on Monday. No explanation for the decision was given.

Charges against Claassens – the alleged triggerman in many of the sham hunts – had earlier been withdrawn after he was given a section 204 indemnity in exchange for his testimony against the others.

Jurisdictional challenge

The M&G understands that the case foundered because prosecutors failed to centralise the case in the Kempton Park Regional Court, raising a possible jurisdictional challenge to the charges. The National Prosecuting Authority's South Gauteng spokesperson, Phindi Louw, said the case could not be centralised because "there were no dockets opened anywhere in the country except in Gauteng", an apparent reference to the fact that a number of the original offences were allegedly committed in North West. She claimed the charges were also withdrawn because the case was "based on circumstantial evidence".

In his guilty plea, Lemtongthai, also known as "Chai", said that he had helped to arrange numerous rhino hunts that, although having a veneer of legitimacy, were actually "a front … to export rhino horn for trade and not for trophies".

South Africa and Swaziland are the only two countries in the world where rhino can legally be hunted for sport. The horns can only be legitimately exported as "personal hunting trophies". In terms of the Convention on International Trade in Endangered Species, the trophies cannot be sold or traded.

One of the syndicate's more ingenious schemes was to recruit young Thai women – some of whom worked in the Gauteng sex industry – to pose as hunters in sham hunts. A number of them were paid R5 000 each to go on a "holiday" in the bush. They would be required to provide their passports to the syndicate. Copies would be emailed to Steyl, who would apply for hunting permits on their behalf.

The women would allegedly be taken to Steyl's North West game farm and made to pose next to the carcasses of freshly killed rhino with a rifle in hand. In interviews, a number of the women denied having shot any rhinos. One said: "It was the first time I see a real rhino. Before, only on TV in Thailand." She remembered the rifle being heavy and difficult to hold.

Another claimed to have cried when she saw the carcass. "[I]t was wrong for them to shoot such a big animal," she said. Others were more callous and one woman posed on the back of a dead rhino, clutching a rifle in one hand and showing a "V" for victory sign with the other.

For shooting

A Gmail account used by Lemtongthai provides a detailed electronic record of some of the transactions. For instance, in just six days between May 20 and May 26 2011, Lemtongthai sent Steyl 18 passports "for shooting".

Records held by provincial nature conservation officials and the department of environmental affairs show that between November 2010 and March 2011 at least 20 hunting permits were issued to Thai women to hunt on Steyl's game farm, Aurora. Xaysavang's hunters accounted for at least 30 of the 73 permits issued in eight months in the Dr Ruth Segomotsi Mompati District.

In his plea, Lemtongthai admitted that the "people on whose behalf the [permit] applications were made were not bona fide hunters and their passports were merely used to fraudulently obtain hunting permits in their names". But, he claimed, none of the hunting outfitters or landowners, including Steyl, were aware of the fraud. The video footage, emails and invoices for rhino trophies – billed at between R60 000 and R65 000 per kilogram of horn – appear to contradict his claim.

The 25 minutes and 35 seconds of video footage show a hunt that took place in January 2011. It is one of dozens of videos and hundreds of photographs that Lemtongthai and other members of the syndicate took. The photographs and video clips were stored on computers in South Africa and Thailand. Some appear to have been widely circulated by members of the syndicate.

The video begins with Lemtongthai adjusting a GoPro camera strapped to Steyl's head and giving him a thumbs up. A rifle barrel distorted by the lens comes into view. As the camera pans it picks out other faces, including Claassens, Chunchom, an unidentified tracker and the "hunter" in whose name the hunting permit had been issued, Nimit Wongprajan.

The only people who appear to be armed are Steyl and Claassens. Wongprajan is only seen holding a rifle in subsequent clips – after the rhino has been killed and propped up for the trophy pictures.

Ragged breaths

Twenty-one minutes into the video, Steyl, wearing the GoPro on his head, fires a shot at a rhino that appears to be dozing under a tree. A few seconds later a desperate keening sound, like a baby crying or a pig being slaughtered, can be heard as the animal thrashes wildly in a desperate battle to stand. It takes five shots, including one from Claassens, before the animal collapses and slowly rolls on to its side. But even then it appears to still be alive. Ragged breaths from its nostrils can be seen displacing dust near its head with its hind leg kicking its final death throws.

Steyl approaches the animal, takes off the GoPro and walks away. As he turns, the camera shows Wongprajan in the background. He is not carrying a rifle. Steyl looks down at the camera, fiddling for the off button.

Subsequent video clips show Wongprajan, Chunchom and Lemtongthai taking turns posing next to the animal holding a rifle.

In terms of South Africa's hunting regulations, the person in whose name a hunting permit is issued is required to fire the first shot. If the hunter wounds the animal or if he is in danger, the professional accompanying him can shoot.

Documents show that in May 2011 Steyl invoiced Nimit for R208 000 for the horns. Four days later the money was transferred from a Bangkok bank account held in Lemtongthai's name to an account at a Johannesburg branch of the Bank of Athens. The beneficiary was Steyl Game CC.

Efforts to contact Steyl and Claassens proved unsuccessful this week.

The Kingpin

The Xaysavang Trading Export-Import company, from which the "Xaysavang syndicate" takes its name, is headquartered in a small provincial town on the banks of the Mekong River in central Laos.

For nearly a decade the company has been implicated in widescale international wildlife trafficking and its head, Vixay Keosavang, has been described by investigators based in neighbouring Thailand as the "Mr Big in Laos".

Shipments of illegal ivory destined for the company have been intercepted in Nairobi and Bangkok. One document seen by the Mail & Guardian illustrates the scale of the company's activities. It is a sale agreement signed by Keosavang and a Vietnamese company, Thaison FC, in which he agrees to supply them with 100 000 live animals including endangered yellow-headed temple turtles, king cobras, water monitors and rat snakes.

Investigations by the M&G in Vietnam and Laos show the extent of Keosavang's political connection in Laos, a one-party communist state that is routinely listed among the world's most corrupt countries by the corruption watchdog, Transparency International.

A former soldier in the Lao People's Army, Keosavang is said to maintain ties with the country's military intelligence structures and has held a senior position in a state-run company with interests in construction and international trade. He has headed the foreign cooperation division in the provincial government of Bolikhamxay province and served as secretary to the provincial chairperson. His business card lists him as vice-president of the Laos national swimming and boxing committees, and the Bolikhamxay chamber of commerce and industry.

In 2004, there were reports that Keosavang accompanied the then Laotian deputy prime minister, Bouasone Bouphavanh, on an official state visit to Vietnam.

Chumlong Lemtongthai, a Thai, is seen as Keosavang's "lieutenant" and in a number of documents is a listed as a "director" of Xaysavang Trading Export Import. In his plea this week, he claimed he was merely an "agent" for the company.

He said Keosavang had sent him to South Africa to "enquire about the purchasing of lion bones" which are increasingly being sold as an alternative to tiger bones on the medicinal black markets of south-east Asia. Later, he said, he saw advertisement for "the hunting of the big five including rhino" and informed Keosavang who said he would "fund any trade in rhino horn". – Julian Rademeyer