S.S.P. Chowrasia held the clubhouse lead for several hours before Rock surpassed him with a birdie on his final hole. Chowrasia, an Indian Tour regular, shot a 5-under 65 and was alone in second place.
Rock, 29, enjoyed a near-spotless round of seven birdies and just one bogey for his personal low score on the European Tour. It was a far cry from his experience last year, when Rock withdrew before the first round after falling ill with chicken pox.
'My name usually comes off the leaderboard quite quickly once it gets on there,' he said, 'so at least it will stay up overnight. I have been working hard on my game so hopefully this is a change for the better.'
Similar wishes were not answered for Chowrasia, who set the morning pace with seven birdies and two bogeys only to be bested by Rock's afternoon performance.
'My feel wasn't good yesterday, I don't know why,' Chowrasia said. 'But this morning, I hit good shots and hit some good putts in practice and suddenly my feel came back.'
Edward Loar, Kane Webber and Rafael Echenique shared third place at 4-under 68. Former champions Alastair Forsyth and Wei-Tze Yeh were a shot further back at 69 along with Ricardo Gonzalez, Mark Foster and Mikko Ilonen.
The leaderboard was most notable for the names that couldn't be found near the top, like European Ryder Cup teammates Darren Clarke and Lee Westwood.
Clarke opened with a 74 and was tied for 67th place with 18 others. Westwood, the 1997 champion, carded a 75 and joined 21 other players in a tie for 85th place, including former U.S. Open champion Michael Campbell.
Two-time Malaysian Open winner Thongchai Jaidee and last year's Asian Tour Order of Merit champion, Jeev Milkha Singh, shot matching 1-under 71s and were tied for 21st place.
Last year's event was shortened to 54 holes due to persistent lightning storms at Kuala Lumpur Golf & Country Club. Charlie Wi, who won by a shot over Jaidee, is not in the field this week to defend his only European Tour title.
Thursday's round was played under hot, humid conditions. The weather forecast calls for possible thunderstorms over the weekend.
The Golf Channel will have coverage of all four rounds beginning at 9:30 a.m. (ET). Next week is the Indonesian Open, which was won by Simon Dyson last year.