The unmistakable sound of Cantonese may be joy to the ears of some (see previous feature) but it is not a language you might expect to hear widely spoken on the streets of a small Cambodian town. But the rows of illegal football-betting shops that line the frontier settlement of Poipet, just across the border from Thailand, are exclusively Chinese-owned. Furthermore, they are part of a multinational chain of illicit football-gambling operations that stretches across Southeast Asia to the mainland.

The influx of Chinese and ethnic Chinese from Singapore and Malaysia has turned Poipet into a gambling boomtown with an unlikely international flavour. And the football-betting outlets are no small businesses - they cater to Thais thousands of whom who cross the border at weekends to gamble in casinos that are allowed to operate legally here, as well as to visitors from China, South Korea and Malaysia.

With football betting illegal in Cambodia, and across much of Southeast Asia and China, the shops in Poipet form a vital link in an underground industry that some experts estimate to be worth more than HK$10 billion a year. And it is those immense profits that are believed to be fuelling what the acting president of the Asian Football Confederation, Zhang Jilong, described in February as the "pandemic" of match-fixing plaguing football leagues around the world.

Such is the scale of the problem in the mainland that star player David Beckham's arrival in Beijing last month as the newly appointed ambassador for mainland football was seen by many as a desperate attempt by the authorities to restore the image of the sport after years of match-rigging, which has eroded the faith of fans. In February, an investigation resulted in 33 officials and players being banned from the game for life. Last year, China's top referee, Lu Jun, was jailed for accepting bribes, along with a number of other referees and officials.

It is easy to prove the ties between the shop-front bookmakers who operate openly in the shadows of the casinos in Poipet and the criminal gambling syndicates in China, Singapore, Vietnam and the Philippines. It is those gangs that both Europol, the European Union's law enforcement agency, and Fifa, the governing body of world football, believe are behind the recent match-fixing scandals in Asia and Europe.

At a football gambling shop named the senior staff are all from Guangdong province. They sit behind a high counter staring at computer screens while local teenage girls help punters place bets on matches that range from big-ticket European fixtures to obscure games such as an under-16s clash between Greece and Kazakhstan. When Post Magazine asks to make a wager on the English Premier League game Swansea vs Arsenal, the bet is placed via a Chinese-language website that is most certainly not that of the Hong Kong Jockey Club, which is allowed by the SAR's government to take bets on football matches.

"People from Macau were the first Chinese who came to Poipet," says a 30-year-old woman from Guangzhou working in who asks to be referred to only by her nickname, Xiaoli. "They arrived in 2008. Then people from Guangdong followed because they wanted to cash in as well.

"I came four years ago because I heard there were opportunities here. Then I told other members of my family that it is good business and some of them came, too."

"All the gambling shops are owned by Chinese or ethnic Chinese from Singapore or Malaysia," says Rothana, a cheerful 25-year-old Cambodian whose shop,, is decorated with the logos of Manchester United and Liverpool. "My boss is from Singapore. He sent me up here from Phnom Penh [the Cambodian capital] eight months ago to open this place.

"Of course we are operating illegally; soccer gambling is against the law. But we pay the police to let us operate."

Just as the shops are owned by Chinese, so the Thais and Cambodians working in them are mainly ethnic Chinese.

Says Xiaoli: "A lot of the families who came here from Guangdong have family ties in Thailand and Cambodia. So we employ them rather than the locals in Poipet. It's safer for us, because we know we can trust them."

Most of the football-betting shops look like internet cafes, aside from the television screens broadcasting the big European games live. Punters sit in front of computers 24 hours a day placing bets and tracking the games they are betting on.

"We make about HK$26,000 a night," claims Rothana.

Poipet's walk-in customers generate only a tiny fraction of the massive profits made by the gambling gangs, though. It is the online betting sites in the mainland, and the Philippines, where the real money is made. The shops in Poipet are linked back to them - which is why our bet was placed on a Chinese-language site - and they cater to punters in countries where betting is illegal and where opening an online account is the easiest way to circumvent the law.

Football bets are made according to what has become known as the Asian handicap system. Teams are handicapped according to their form, so a top team playing a lesser one will be given a handicap of 2.5 or three, meaning they must win by three goals or more for a punter betting on them to win.

"The Asian handicap system was invented in Indonesia after the 1990 World Cup, when football betting really began to become popular in Asia. It's a way of creating viable odds for the bookmakers," says Visanu Vongsinsirikul, an expert in football betting at the Centre for Gambling Studies at Bangkok's Chulalongkorn University.

It is a system that is now employed in Europe, too.

More than anything, though, it is "online gambling [that] has really enhanced the growth in football betting, and that's because it allows for live betting", says Visanu. "Gamblers can bet while the match is ongoing; on who will get the next yellow card or corner or goal."

Live betting has been a boon for match-fixing syndicates. Agents for match-fixing gangs contact corruptible officials and players, and arrange for games to be rigged. Then, while they are being played, hundreds of people place bets online, knowing already which team will win, or when a penalty is likely to be awarded. Wagers can be as much as HK$350,000. Visanu estimates that in Thailand alone, where football gambling is illegal, the industry is worth HK$1 billion annually, and that that amounts to just 10 per cent of the profits generated across Asia each year.

In February, the true extent of match-fixing in football became apparent when Europol announced the results of an 18-month investigation. It revealed that a staggering 680 games in 30 countries between 2008 and 2011 were likely to have been rigged. Those matches included World Cup qualifiers and Champions League games. Of those suspect games, 380 were played in Europe, the other 300 across Asia, Africa and Central and South America.

Both Europol and Fifa believe Tan Seet Eng, better known as Dan Tan, a 48-year-old ethnic Chinese Singaporean, is the man behind much of the match-fixing. His involvement became known after references to him as "Il Boss" emerged in a 2011 Italian police investigation into games that had been rigged in Italy's lower divisions.

It is alleged that Tan employs former Eastern European footballers to pay officials and players to throw games, before tipping off online gambling syndicates in the mainland, Vietnam and the Philippines. But with there being no extradition treaty between Singapore and Italy and no evidence that Tan has committed any crimes in Singapore, he remains at liberty.

Match-fixing is now so widespread that many punters are desperate to find out which games have been rigged. "Guy", a middle-aged Thai businessman in Bangkok, is a self-confessed soccer gambling addict who bets up to HK$50,000 a month on matches around the world, either online or at illegal bookmakers.

"A lot of people pay for inside information. I used to pay a man 10,000 baht [HK$2,650] a week to find out which games in the Brazilian league had been fixed," he says. "He wasn't always right, but he was sometimes."

Not all Chinese in Poipet are here to run gambling operations. Some are punters, including a boisterous group from Kunming, Yunnan province, in the Genting Casino, surrounded by local women.

"We're here to play," one laughs. "It's cheaper for us to come here than to go to Macau."

Under an agreement reached in the early 1990s, Poipet is one of the few places in Cambodia where casinos can operate legally, although Cambodian nationals are forbidden from gambling in them. Inside those casinos are rooms where access is by fingerprint scanner only and which are rented out as bases for online betting. In the lobby of the Genting Casino, adverts in English and Chinese offer space to those wanting to set up shop. Elsewhere in the casino, uniquely Chinese games such as fan tan and tai sai are being played for online punters in the mainland, where all gambling is illegal. Cameras film croupiers operating at tables devoid of gamblers and with Chinese characters on them, a clear indication of who these games are aimed at, for broadcast live on the internet.

While the actual casinos are permitted, almost everything else in Poipet is illegal, starting with the Cambodian border guards who asked us for a "tip" when we crossed the frontier. Even the Genting Casino here is a fake; the real Genting Group is a Malaysian conglomerate that owns casinos around the world and sponsors England's Aston Villa Football Club. The casino in Poipet has simply appropriated its name to draw in punters. Like all the other casinos here, it is a shabby operation that bears no resemblance to the glitzy, theme park-like establishments of Macau and Las Vegas.

In fact, nothing about Poipet is remotely glamorous, despite the fact that the profits from the gambling trade mean it is now larger than the nearby provincial capital, Sisophon. Separated from Thailand by a fetid, rubbish-strewn river, Poipet's filthy streets coat everyone and everything in yellow dust. Outside the casinos and betting shops, barefoot children beg while prostitutes prowl for customers and the motorbike drivers who act as taxis offer drugs at knockdown prices.

"It's a lawless place and scary because of that," says Pan, a Thai man who runs a bar in Poipet. "There aren't many police here, so if you have a problem you can't count on them to solve it. When you rent a bar in Thailand, you have to pay the police as well as your landlord. But in Thailand, the police will look after you. That doesn't happen here, so I try very hard not to have any problems."

Few of the Chinese migrants appear enamoured of Poipet.

"I don't like it," says Xiaoli. "It's hot and dirty and just a gambling town. There's nothing here except casinos and football-betting shops. My husband is with me, but my two children are back at home in Guangzhou because it's not good for them here."

Poipet is certain to continue to be a magnet for the gambling gangs of the mainland and Southeast Asia for as long as its authorities are viewed as having no interest in regulating the businesses that flourish here.

"I don't think the locals care that so many Chinese are here now," says Pan. "They're bringing in money to Poipet and as long as that continues, everyone is happy."