PHUKET, Thailand (AP) -- When a German tourist refused to surrender his passport as collateral at a car rental stand along a popular beach in the Thai resort city of Phuket, the woman behind the counter pulled out a bag full of passport books to prove he could trust her.
But the tourist, Falko Tillwich, was insistent. "I said absolutely not ... no way," he recalled, and later handed over his driver's license instead.
Tillwich's concern: losing vital travel documents, or worse -- having them stolen by criminal syndicates that are exploiting lax law enforcement and corrupt police here to support a global network of human smugglers, fugitives and sometimes, terrorists.
Those worries were heightened this week after investigations into Malaysian jetliner that went missing March 8 with 239 people aboard revealed two Iranian citizens had boarded the flight with passports stolen from tourists in Thailand.
Investigators say it was unlikely the two men had links to terrorism and appeared to be illegal migrants trying to get to Europe. However, Malaysian Prime Minister Najib Razak said Saturday authorities were re-examining the list of crew and passengers after deciding the plane had deliberately changed course after taking off from Kuala Lumpur on the way to Beijing.
Passport theft is "a very big and critical problem in Thailand," said police Maj. Gen. Apichart Suribunya, who serves as Thailand's Interpol director. "It is a problem that Interpol, the United Nations and the international community have been trying to solve for years."
So far, with limited success.
Thailand's sapphire blue waters, wildlife parks, delicious cuisine and raunchy red light districts have attracted tourists for decades. Last year alone, 22 million foreign visitors made the trip. That means "there are more passports to steal in Thailand than other countries in the region," said Clive Williams, a counterterrorism expert at Australia's Macquarie University.
Phuket is one of Thailand's tourism honeypots. Tourists flock here in droves each year for its sun, sand and laid back ambience. And some, like Italian Luigi Maraldi, lose their passports along the way.
Maraldi hired a hired a motorbike on Phuket last year. When he returned to the shop to retrieve his passport, he was told it had been given away to someone who looked like him.
His passport, along with another stolen in Phuket two years earlier, was used to board the ill-fated flight undetected, revealing startling shortcomings in the security of international travel.
Interpol says it maintains a global database of 40 million lost or stolen travel documents, but only a handful of countries actually check it before allowing passengers aboard flights. Malaysia and Thailand are not among them.
Apichart said accessing the database is not complicated, but Thai authorities use it only when travelers are deemed suspicious. It can also be time-consuming, he said, and the government has been keen to facilitate the lucrative tourism industry and ensure immigration lines aren't clogged.
"This is something we have to rethink," Apichart said.
The global intelligence company Stratfor said that passport fraud is common among human traffickers, drug smugglers, arms merchants, money launderers, fugitives and pedophiles -- many of whom end up in Thailand. "Only a very small percentage," of those involved in the underground trade have terror links, Stratfor said.
Nevertheless, the threat remains a concern. After the Sept. 11 attacks, Thailand -- under pressure from Western governments -- vowed to crack down.
In 2004, police arrested a Bangladeshi who allegedly supplied forged passports to al-Qaida-linked terrorists, including the mastermind of the 2002 Bali attacks. In 2010, authorities nabbed Pakistani Muhammad Butt, who police believe provided false passports to suspects in the Madrid train bombings.
Two years later, Thai officers arrested Parknejed Seyed Ramin for alleged involvement in a passport racket that was thought to have aided suspects in a bomb plot discovered in Bangkok on Valentine's Day the same year. Police said Ramin's gang had been running a lucrative, 5-year-old forgery business worth millions of dollars.
Governments like the United States have fought back by embedding digital chips inside passports that contain a photo of the passport holder and information about the owner. Stratfor said that has made it tougher to alter photos, but chips can still be hacked.
In Thailand, passport forgers now use advanced technology, and their clients can evade capture by selling them to lookalikes who resemble the owners.
A senior Thai intelligence official, who has spent years hunting down passport theft rings, said investigators are currently tracking about 10 major syndicates in Thailand.
Most were run by nationals from Pakistan, India, Iran or Central Asia he said, for clients that are mostly illegal migrants. The fact that travel documents are often stolen or forged in one country and used in another, though, "makes it hard for the governments to follow and arrest them," he said.
In Phuket this week, police called meetings with dozens of owners of motorbike rental shops and told them to take copies of passports instead of the originals. It was unclear, though, how or whether they would enforce it.
Associated Press writer Todd Pitman contributed to this report from Bangkok.