Ruffels carded a bogey-free six-under-par 66 at the Kuala Lumpar Golf and Country Club to rocket from 26th to a tie for sixth after her second round on Friday.
The 23-year-old collected three birdies on each nine, including one on last, to ice her round and soar to nine under for the championship.
Ruffels started the week third in the race for rookie-of-the-year honours but could conceivably hit the lead with a maiden LPGA Tour victory on Sunday.
The former national junior tennis No.1 is the leading Australian, sitting three strokes behind Swedish halfway leader Maja Stark.
Stark burst to the front of the pack with four straight birdies to start her back nine, eventually signing for a 66 and a one-stroke lead at 12 under over American Marina Alex, Koreans Narin An and Haeran Ryu and Taiwan's Wei-Ling Hsu.
Alex rattled off six birdies and an eagle in firing the day's low round, an eight-under 64 to surge to 11 under for the tournament.
An (67), Hsu (68) and Ryu (69) are also 11 under, one ahead of Korean Hye-Jin Choi (66) and China's world No.4 Ruoning Yin (67).
Sweden's Maja Stark has a one stroke lead at halfway in the Maybank Championship in Malaysia. (AP PHOTO)
Ruffels is poised nicely one shot further back.
First-round frontrunner Mao Saigo, who leads the rookie-of-the-year race from Jin Hee Im and Ruffels, wobbled with a second-round 74 to drop to a share of 13th at seven under.
Seeking back-to-back victories after winning the Ladies BMW Championship last week in Korea, world No.5 Hannah Green is tied for 27th with fellow Australian Grace Kim.
Green followed up her opening round of 71 with a 69 to climb to four under as Kim could only manage a one-over 73.
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