An air-conditioning workman was charged yesterday with the 2005 murder of a Thai businesswoman whose body was found on top of an air-conditioning unit on the 33rd floor of Revenue Tower. So Kam-tong, 25, a Hongkonger who lives in Tai Po, appeared at Eastern Court yesterday charged with murdering Charitar Kamolnoranath on October 12, 2005, at the government building in Wan Chai. No plea was taken. Acting Principal Magistrate Bina Chainrai adjourned the case to February 24 to provide time for two psychiatric reports and a medical report to be prepared to determine So's psychiatric background and whether he has hearing problems. So is being remanded in custody at Siu Lam Psychiatric Centre. The defendant remained silent in court, even when Ms Chainrai addressed him. So refused to talk with lawyers and, after indicating that he wished not to have their representation, also refused to sign a document stating his wish, a lawyer who was assigned to represent him said. The body of Charitar, 40, was found three metres off the ground, on top of an air-conditioning unit, in the machine room of the Environmental Protection Department office on the 33rd floor of Revenue Tower on October 24, 12 days after she disappeared during a visit to Hong Kong - and 12 days after the date when So was alleged to have killed her. She was found with her hands bound and with a stab wound. Her handbag, passport, cash and credit cards, two mobile phones and a pair of sunglasses were missing.