THE discovery of six slaughtered elephants last month in two of Thailand's national parks has exposed a nasty secret.

The discovery has exposed a nasty secret about the country's ubiquitous elephant tourism industry.

Dutch national Edwin Wiek, founder of the Wildlife Friends Foundation Thailand, jumped on the wild elephants' gruesome demise in Kaeng Krachan and Kiu Buri parks to draw attention to a lucrative trade in baby elephants that has been carried out with the apparent compliance of government officials.

In an article in The Nation newspaper on January 24, Wiek said the six elephants had been killed to get their babies, not for elephant meat and ivory as claimed by government officials.

He argued that the incident demonstrated that the trade in baby pachyderms was no longer just a cross-border business with Burma, but that poachers were now targeting Thailand's own depleted herd of fewer than 2000 wild elephant.

Based on his own investigations, Wiek estimated that two to three baby elephants were poached from the wild a week.

A baby elephant can fetch up to 1 million baht ($A30,500) at camps in Ayutthaya, Chiang Mai, Hua Hin, Pattaya and Phuket, where they are trained to perform tricks and provide rides for tourists.

Foreign tourists might think twice about supporting the elephant business with their money if they were aware that many of animals had been poached from the wild and their parents slaughtered, Wiek said.

After the article was published, Wiek's animal sanctuary in Phetchaburi province was raided on February 13 by 70 armed officials from the National Parks, Wildlife and Plant Conservation Department.

The officials demanded to see ownership documents for some 400 animals kept at the wildlife rescue charity, established in 2001.

Although Wiek had proper ownership documents for his six pachyderms, national park officials claimed that 103 smaller mammals lacked proper documentation and vowed to confiscate them.

The animal sanctuary was still under armed guard this week.

Wiek has claimed that the raid was revenge for his exposure of the authorities' complacency, if not complicity, in a booming business in baby elephant trafficking.

Thai authorities claim otherwise.

"The discovery of the six dead elephants had nothing to do with the raid on Wiek's place," said Damrong Phidej, director-general of the National Parks, Wildlife and Plant Conservation Department.

"There are so many of these charities and none of them have proper paperwork for the animals, so we are trying to straighten it out a bit," Damrong said.