Thai communications authorities have blocked a Web page, run by a U.S. university publisher, that promotes an unauthorized biography of King Bhumibol Adulyadej.
The page on the Web site of the Yale University Press contains a short summary of the book "The King Never Smiles," scheduled to be to be published on May 29.
The book, by American journalist Paul Handley, is the first comprehensive biography in English of the 79-year-old king, the world's longest reigning monarch. The country already has banned imports of the book, which the royal family considers insulting to the king.
Thailand's king is revered by most Thais, and words and behavior considered insulting to the monarchy are punishable by up to 15 years in prison, although the crime has rarely been prosecuted in recent years.
In a statement, Yale University Press said it was aware of the concerns, but stood by the author. It said that the book has been thoroughly vetted by leading scholars and Yale faculty and that the author has expertise, having spent 13 years living in Thailand and reporting on the region.
According to the Royal Thai Police Web site, some 32,467 Web sites have been reported as illicit since censorship of the Internet was launched in April 2002. More than half are categorized as pornographic, and 3,571, or 11 percent as a "Threat to National Security."
It does not say how many concern the monarchy.
Prominent sites blocked through the use of filtering software include several sympathetic to a Muslim separatist movement that is currently engaged in an insurgency in Thailand's southernmost provinces.