A Thai court jailed a former equity trader for four years on Tuesday for posting false Internet messages about the king\'s health that sent stocks plunging in 2009, an official said. Katha Pajariyapong, 39, was found guilty of three counts of breaching the kingdom\'s controversial computer crime laws in messages posted under his username on the Sameskybooks.org Internet forum. The messages on October 14-15 in 2009 were followed by a slump in the Thai stock market -- which at one stage plunged by more than eight per cent -- over rumours about the condition of the revered but ageing King Bhumibol Adulyadej. The court found Katha, of brokerage company KT ZMICO, guilty despite his denials during trial, a court official told AFP, adding \"he is sentenced to four years in jail immediately\". An initial sentence of six years was reduced by a third because he had confessed when he was first charged three years ago, despite later pleading not guilty at trial. The monarchy is a highly sensitive topic in politically turbulent Thailand. The 85-year-old king, who is revered as a demi-god by many Thais, has been hospitalised since September 2009. Soon after Katha was charged a media rights group called for the dismissal of the \"baseless\" charges against him, and two others. The trio were charged under section 14 of the computer crime act which punishes anyone found guilty of spreading \"false information into the computer system\" that damages national security or causes the public to panic. Thailand also has a strict lese majeste law under which insulting or defaming any members of the royal family is punishable by up to 15 years in jail. The Internet has become one of the key battlegrounds for Thailand\'s complex political debates with social networks surging in popularity over the last few years. Tens of thousands of web pages have been removed from the Internet in recent years from for allegedly insulting the monarchy.