The ministry's Division of Medical Registration handled 85 cases of people masquerading as licensed medical doctors in 2005, said Dr Tares Krassanairawiwong, head of the division.

Tares said the number of cases in 2004 was far higher than in 2005, but did not have the exact figures during a telephone interview with The Nation.

However, the number of the overall complaints filed against private medical institutions was much higher in 2005, he said.

The bogus doctor cases made up the majority of the 519 complaints.

In most cases, there were two major types of culprits impersonating qualified doctors, he said.

Usually, if it was a private clinic in a small town upcountry, the fake doctor turned out to be a person in a related profession - but not a real doctor, he said. Fake doctors found in large cities like Bangkok and Chiang Mai were found to be individuals who knew nothing about medicine, said Tares, adding that they worked shifts when genuine doctors were not on duty.

"In big cities there are many medical doctors and even they don't seem to recognise each other," said Tares.

The complaints leading to the arrest of the fake doctors came from both their patients and real medical professionals who realised they were acting abnormally, he said.

"Unauthorised doctors usually worked in unauthorised clinics," said the doctor. Only a few were found working at authorised clinics and private hospitals mixing together with real doctors.

To make sure they are not fooled, Tares has urged people to take a careful look on the wall of the clinic.

It is required by law for an authorised clinic to place a valid "medical institution" licence on the wall with the photo of the doctor licensed to open the clinic, plus a photo of the doctors on duty on the wall in the diagnosis room, and the receipt of the annual fee for clinic's operation.