Gavin Green produced a brilliant run of four birdies around the turn to post a 68 and set the clubhouse target on a weather-delayed day two of the D+D Real Czech Masters.
The Malaysian entered the day in a four-way tie for the lead at Albatross Golf Resort but made seven birdies on his way to a 12 under par 36-hole total and a two-shot lead.
Fellow overnight leader Thomas Pieters was among the closest challengers alongside three-time Major Championship winner Padraig Harrington and last season's Road to Oman champion Tapio Pulkkanen.
Swede Peter Hanson and Scotland's Scott Jamieson were then at nine under, a shot clear of 2014 champion Jamie Donaldson, Thai Phachara Khongwatmai and England's Callum Tarren.
Green's only top ten in 33 European Tour appearances so far was a runner-up finish at last season's Hero Indian Open as he looks to become the first Malaysian winner in Tour history.
Belgian Pieters won this event in 2015 and a second-placed finish the following year helped him earn a Captain's Pick for the Ryder Cup, something he will once again have his eye on ahead of Thomas Bjørn's selections on September 5.
Just under 90 minutes was lost due to the threat of lightning early in the morning but that did not prove too much of a distraction for the field on another low-scoring day.
Finn Pulkkanen was out in the very first group of the day off the tenth and he birdied his opening hole to quickly move into a share of the lead.
Pieters had dropped out of a share of top spot by bogeying the 14th when he restarted after the lightning delay but he bounced straight back on the next.
Pulkkanen edged ahead from four feet on the first before Pieters joined him after a tee-shot to seven feet on the par three 16th.
Green was the next man to join the lead as he took advantage of the par five 12th, with Pulkkanen bogeying the third but picking the shot straight back up.
Green birdied the 14th from 18 feet and a wonderful approach into the next gave him a two-shot lead before Pieters spun his approach into the second close to cut the gap.
Finding the water on the 16th led to a Green double-bogey to hand Pieters the initiative and the reigning Asian Tour Order of Merit champion dropped another shot on the next.
Pieters holed a 20-footer on the fifth to move two ahead but Green was still fighting and holed a 15-footer on the 18th and made the most of the par five first to get back into double figures.
Pulkkanen birdied the par five ninth to set the target but Green had momentum once more and a six-footer on the second put him in share of the lead.
A tee-shot to tap-in range on the next meant that Green was ahead and with Pieters bogeying the eighth after a poor second, the lead was two shots.
Harrington made a birdie and a bogey before the stoppage but a stunning approach to the 18th moved him back into red numbers. Back-to-back birdies on the fifth and sixth edged the Irishman further up the leaderboard and he was into double figures with a 15-foot putt on the ninth.
Hanson started his round with nine straight pars but holed a monster putt on the first for eagle and another lengthy effort on the sixth brought a birdie to put him right in the mix.
Jamieson carded six birdies and two bogeys in his roller coaster of a 68, while Welshman Donaldson was bogey-free in making the same score, picking up shots on the 11th, 18th, first and fourth.
Khongwatmai also completed a blemish-free effort, making gains on the first, ninth, tenth, 12th and 18th, with Tarren carding a level par 72.
Italy's Andrea Pavan was two under after five holes to sit at nine under, with German Alexander Knappe and England's Lee Slattery moving into the group behind early in their rounds.
