A POLICE constable acted as a pimp for a man who responded to his advertisement in a newspaper, the District Court heard yesterday. Lo Man-wai, 27, who was attached to Happy Valley police station at the time of the offences, pleaded guilty to living on the earnings of prostitution of another and attempting to procure prostitution of another person. He was jailed for three months. Prosecutor Mr Stephen Llewellyn offered no evidence against Lo on charges of attempting to live on the earnings of prostitution of another and doing an act tending and intended to pervert the course of public justice. The court heard that in December 1991, Mr Chan Sheung-tak, 22, answered a newspaper advertisement worded along the lines of: ''Handsome male, tall and strong, serves men and women. Apprentice required.'' Lo arranged to meet him later that day. They went to a restaurant where Lo told Mr Chan the job would require him to provide sexual services for male and female customers in return for about $500 on each occasion, Mr Llewellyn said. Lo said he himself would get a commission of $100 or $200 depending on the amount paid by the customer. On about 12 occasions between December 1991 and February last year, Lo introduced male customers to Mr Chan, who rendered sexual services in return for money, counsel said. Each time, $100 was deposited into Lo's bank account as commission. The court heard Lo's activities came to light on March 3 last year when police raided a flat in Yau Ma Tei, where they found Lo sitting astride Mr Cheung Ping-wah, 34, showing him how to massage customers. Both were wearing only towels. Mr Llewellyn said Mr Cheung had answered an advertisement in a bid to secure the services of a prostitute. But Lo later attempted to procure Mr Cheung to provide prostitution services for male and female customers at a fee of $500 to $600 and $800 respectively, he said. Mr Cheung had been told $200 of the payment would go to Lo as commission and clients would be introduced to him within three or four days. Lo's counsel, Mr David MacKenzie-Ross, said his client had entered into an ''amateurish enterprise'' to help out his 29-year-old brother, who was having financial troubles. But Judge Chua suspected Lo committed the offence not only for profit, but also for his own sexual satisfaction. She said she felt sympathy because the matter had been hanging over Lo's head for the past year and his conviction ended a promising career. According to his police file, Lo, who joined the force in 1983 and had been suspended since his arrest, was an alert and hardworking officer. Lo is expected to appeal against sentence.