Charl Schwartzel's second successive round of seven-under-par 65 gave him a four-shot clubhouse lead at the Thailand Golf Championship.
The 2011 Masters winner appeared to have recovered from the rib injury that has affected his swing for much of the season and was on 14-under-par 130 after 36 bogey-free holes in the $1-million Asian Tour event.
Swede Daniel Chopra had his second successive 67 to lie four shots behind Schwartzel before second-round play was suspended due to darkness.
Darren Clarke sits on two under at the half-way stage after posting a level par 72 in his second round.
Twenty-five players will return early on Saturday to finish their rounds.
After a 90-minute delay due to a lightning storm, last year's runner-up Schwartzel rushed to the 18th tee box to complete his round in semi-darkness to earn a few precious extra hours in bed on Saturday.
"We were running to finish. I didn't want to come back at 5am to play one hole - (I'm) happy to have a bit of a sleep," the 28-year-old South African said.
"It has been really solid. I've put two great rounds together. I hit the ball nicely and gave myself a lot of chances.
"It is still a long way to go. It's half the job done. From my side, I just have to keep playing."
Asian Tour rookie Masanori Kobayashi of Japan briefly held the lead before signing for a five-under-par 67 to drop five shots off the lead.
Sergio Garcia was three shots further back with big-hitting Scott Hend of Australia after the Spaniard carded his second straight 69.
Garcia turned in 36 but bounced back with three birdies in the closing five holes.
"I'm in a decent position. I would like to do better for the weekend but hopefully if I get a good weekend then I might have a chance," said Garcia.
Joining him on 138 was Masters champion Bubba Watson who sank three birdies in his opening eight holes but could not keep the momentum going and settled for a two-under-par 70.
Defending champion Lee Westwood was left to lament his poor putting after carding a three-under-par 69 to fall nine shots off the lead.
"Just okay, played alright. I wasn't making anything," the world number six said.
"I've made nothing the first two days and left too many out there - missed too many short ones which is the main difference really," said the Englishman.