A man was convicted yesterday of blackmailing a Hong Kong-based diplomat at gunpoint and holding him prisoner in Cambodia. Lang Shit-yi, 42, threatened to kill Cheung Ching-biu, an economic and trade envoy for Dominica, if he failed to hand over $500,000, the District Court heard. Lang claimed to be a mainland public security officer and pistol-whipped Mr Cheung in a Phnom Penh hotel. He received $300,000 from the victim but was arrested on his arrival at Kai Tak in January. Deputy Judge Barnabas Fung Wah found Lang guilty of two charges of blackmail and four charges of dealing with proceeds of an indictable offence. The judge adjourned sentencing until September 10 for reports.