"Hohenlohe died on Tuesday. We've sent all the details to the Swiss Embassy," said a prison official, who asked not to be named.

"He was here on charges of possessing false documents," the official said without elaborating.

Christoph's brother, Hubertus von Hohenlohe, said Christoph arrived in Thailand in mid-July on a transit visa but had overstayed by a day after missing his flight.

Hohenlohe, 49, from Liechtenstein, apparently altered the date on his visa, leading to his arrest on July 29 at Bangkok International Airport.

Hubertus said his brother had been denied bail twice. An autopsy was under way to determine the nature of Hohenlohe's death.

"It's strange," Hubertus said after arriving in Bangkok on Sunday to help get his brother out of custody.

In an interview with Italian newspaper Corriere Della Sera, he said their mother visited Christoph in jail on Saturday, and he was in a room without mattresses.

The Nation, DPA