A COUPLE chatting on Repulse Bay beach at 5 am one day last summer were threatened by an illegal immigrant wielding a 60-centimetre water pipe who snatched a bag containing $1,000, the High Court heard yesterday. Lai Tung had chased Cheung Kwok-wah, 21, but was hit twice on the head with the pipe before the robber escaped, prosecutor Fanny Wong said. A patrolling policeman picked up Cheung shortly afterwards. Cheung was sentenced to 61/2 years' jail after pleading guilty to robbing Wong Yuen-fan of $1,000 and wounding Mr Lai with intent to cause grievous bodily harm on June 7 last year. In mitigation, Sze Kin said Cheung had a clear record. The money had been returned and Lai had suffered only minor injuries. Mr Sze said Cheung had to flee Beijing after the 1989 crackdown. Since then, he had worked as a security guard in Shenzhen. Passing sentence, Deputy Judge Jones said the offences were aggravated because Cheung had threatened the victims and used violence in his escape bid. As this was the third time in three months Cheung had sneaked into Hong Kong, the judge ordered the sentence to start after he finished serving a 15-month jail term for remaining in the territory illegally.