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In most cases, the conviction of a Thai man trafficking rhino horns through a bizarre scheme that involved hiring prostitutes to pose as trophy hunters would have marked the end of the story.

But investigators took an unusual, next step — deciding to "follow the money" that helped bankroll the South African operation, and ultimately winning a court order last year to seize Chumlong Lemtongthai's Thai bank accounts and other assets, including a house worth $142,000, to shut him down.

It was one of an increasing number of cases illustrating how nations are shifting tactics in fighting a global wildlife trafficking market worth up to $23 billion, with the headline-grabbing police raids having little overall effect in halting illicit trades.

The idea is "to pick the pocket of the wildlife traffickers and try to freeze them in their tracks," said Steve Galster, founder of the anti-trafficking Freeland Foundation.

This week, the U.N. General Assembly passed a resolution urging its 193 members to adopt laws making wildlife crimes offences that can trigger money laundering investigations and allow assets to be seized. Existing legal tools for fighting corruption, racketeering and financial crime should also be used to combat traffickers, it said.

Crime gangs are increasingly turning to wildlife smuggling as a lucrative trade. And as they become more sophisticated with their technology and financial arrangements, national customs agents and police have struggled to keep up.

Experts say they need to begin adopting tools commonly used to fight drug lords and other crime kingpins: anti-money laundering techniques and financial investigation.

"We've gone beyond kicking down the door and looking for animals in the back room, to looking at who's the kingpin, who's the transportation coordinator, who ultimately is the vulnerable node in the syndicate without whom the syndicate wouldn't work," said Galster, whose group has teamed up with law enforcement agencies to bring down several trafficking rings in recent years.

A new report this week calls this expanded effort "urgent," given how quickly crime gangs are evolving into cross-border wildlife trades.

Agencies fighting wildlife crime need to conduct financial investigations after every bust — to identify broader criminal networks and uncover criminal proceeds, which can be frozen or confiscated, says the report by the Royal United Services Institute, a British think tank.

Suspicious transactions and bank clients can be "red flagged" for agencies including financial intelligence units to monitor and investigate, the report says. Watch lists of alleged poachers can be shared.

"We've been very slow to recognize wildlife crime as serious transnational organized crime," said Cathy Haenlein, one of the report's authors.

The trafficking epidemic has surged as incomes have risen in Asia. In just the past few months, authorities in Malaysia, Thailand, Vietnam and Indonesia have seized tons of carved ivory, ivory tusks, rhino horns, live pangolins and pangolin scales. The busts included Hong Kong's biggest ivory haul in three decades — a shipment worth nearly $10 million.

But arrests are rarely reported, aside from low level smugglers.

For too long, nations saw wildlife trafficking as an issue for conservationists, Haenlein said. That's allowed traffickers to flourish — using crypto-currency markets to make illicit bulk trades, or stockpiling durable animal parts like pangolin scales or elephant tusks in an attempt to corner the market.

That makes the problem of wildlife trafficking even more acute, giving traffickers perverse incentive to drive down a species' population so that the value of their stockpile goes up even further.

But international investigators and countries' crime units are catching on.

Now, "it's very clear that it is about the money," Haenlein said. And addressing the gap in the chain of smuggling, between those poaching the animals and moving parts and those financing the operations, "could have the potential to change the game."

In January, Interpol said it was going after high-profile Asian traffickers sourcing wildlife from Africa, by drawing expertise from anti-corruption and financial crime units, as well as a digital forensics labs that can extract data from seized electronic equipment.

Some investigators are starting to track sea shipments and compare data on who is booking suspicious cargo transports around the globe.

"A large seizure often has interesting facts around it," said Julian Newman of the Environmental Investigation Agency. For example, "money has been moved somewhere to book a container (for the smuggled goods) and put it on a ship."

Only by following the money will investigators track down the kingpins and financiers, who "never touch the stuff, they handle it through proxies," Newman said.

But countries still aren't moving fast enough to keep up, and they still rarely follow the financial breadcrumbs, according to a July report by the Asia-Pacific Group on Money Laundering and the U.N. Office on Drugs and Crime.

Only a dozen or so governments of 45 surveyed have said they're using financial investigation techniques, seizing assets or pursuing money laundering charges for wildlife cases, the July report said.

"Financial investigations don't come for free or cheap," said Chris Batt, a UNODC adviser who led the study. "You've got to train and commit (investigators) for the cause."

The case of Chumlong, the Thai rhino horn trafficker, was a small but rare victory.

He had been sent to South Africa by a notorious Southeast Asian trafficking syndicate called the Xaysavang network to take advantage of its permit system for professional trophy hunts. Chumlong hired prostitutes to pose as hunters and organized sham expeditions during which 26 rhinos were shot and killed, according to court documents.

The scheme involved doctoring customs papers before shipping the rhino horns to Laos. Once convicted, Chumlong was sentenced to 13 years in South African prison after appeals.

The decision to go after Chumlong's assets was made only in 2016, after agents received training in asset recovery. However, the alleged kingpin of the Xaysavang network, Vixay Keosavang, of Laos, remains at large with a U.S. bounty of $1 million on his head.

Experts say asset seizures can act as powerful deterrents in persuading criminals to avoid getting into the wildlife racket.

They can also offer incentives for governments, who can invest some of those seized assets in the law-enforcement agencies that are working to bring down wildlife crime.

Other examples underscore how much work remains to be done.

In a 2014 case, Freeland helped Thai authorities to identify and freeze $37 million in assets linked to a tiger trafficking ring in the country's northeast. The ringleader remains free, however, and the case has been stalled and might never go to the prosecutor's office.

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Chan reported from Hong Kong. Follow Kelvin Chan at www.twitter.com/chanman and Katy Daigle at www.twitter.com/katydaigle