KEY witnesses who fled Hong Kong to avoid testifying against a triad member were yesterday both sentenced to four months in prison. The pair were caught on March 10 sneaking back across the Chinese border. They said they vanished because they did not want to be witnesses in the case against film producer To Luen-shun, defence counsel John Marray told the court. Tse Wai-kit, 26, and Chan Shing-cheong, 24, were charged with disobedience to a witness order. Deputy Judge Wright said the pair's flight warranted a prison sentence because the charges against To were extremely serious and the two men were the key witnesses. To, 28, was found guilty last month of being a member of the Sun Yee On triad society between 1989 and 1992. But he was acquitted of the more serious charge of being an office bearer of the society. Police had said To ran the Chun Yue Entertainment Production Company which produced a film starring actress Maggie Cheung and singer Jacky Cheung. He also ran a boxing school. Prosecutor Jackson Poon said Tse had alleged the producer had agreed to accept him as a follower, and had invited him to a Tsim Sha Tsui restaurant in May 1992 to undergo an initiation ceremony. The second would-be witness also alleged that To had accepted him as a follower, Mr Poon said. Chan alleged that To taught him a triad poem and arranged for him to work as a valet at some restaurants and nightclubs, the prosecutor said. Both witnesses were offered immunity from prosecution in exchange for their testimony against To. But their refusal to testify has cost them that immunity. ''I understand they will now be charged in respect to what was mentioned in their caution statements,'' Mr Poon said.