A FORMER financial controller for the Hongkong Stock Exchange, Josiah Mah Kin-man, will today appear in Western Court charged with corruption offences. Mah, 42, is charged together with Leung Ping-wah, 41, director of Wah Fei Interior Ltd. Mah is alleged to have accepted a favour from Leung in May 1990 while being an agent of the Stock Exchange in return for influencing the exchange to award decoration work to Leung's company. The favour was to carry out decoration work on a flat belonging to Mah at reduced cost. Leung is charged with offering the favour to Mah. Both defendants are on bail of $50,000.