Worth reading the Straits Times article on this. Essentially, he borrowed money from the bank by pledging his shares and when the share price tanked in 2008, he tried supporting the share price by buying his own shares from the market. Otherwise, he would have faced margin calls. By doing so, he created a false market in the shares.
(In case anyone is wondering, regulatory announcements are public documents and one can copy and paste as appropriate. However, articles written by others are copyrighted and links should be used instead).
REGULATORY ACTIONS BY SGX AND OTHER AUTHORITIES - UPDATES