But despite insisting the injury is only 70% recovered, Thongchai mastered the wetlands and links combination at Jinji Lakes International Golf Club to top the leaderboard alongside the equally impressive Kim.

"I played very solid after a week off last week. I had a good game plan," said Thongchai.

"I was unable to practice on the course before, I only played two holes in the pro-am because the weather was terrible.

"But I hit a lot of fairways and a lot of greens and I made a lot of putts. Over the next few days, if my health stays okay as my arm is getting better and better everyday, I hope to get better and better."

Kim blazed eight birdies and an eagle after following up a third-placed finish at the Luxehills Chengdu Open at the start of April with victory on his home tour last week at the SBS Tomato Open.

"I played very well. It was my third 64 in three weeks," said the 21-year-old.

"I admire Tiger Woods but I also watch KJ Choi and YE Yang and they are my inspiration. Tomorrow I hope to play well again."

Former European Tour rookie of the year Pablo Larrazabal and China's Liang Wen-chong, fresh from winning in Chengdu, had set the early pace at six-under-par but Thongchai quickly cut the lead with four birdies in five holes before the turn.

A superb chip-in eagle from 20 feet off the green at the 14th pushed Thongchai into a share of the lead before impressive approaches into 16 and 17 led to simple birdies putts from inside five feet.

"I hope this week will be a very good week for me," he added.

"Last week was very hard for me having to withdraw.

"But I have had a few days' rest and this week and next week in Korea are very important for me as if I can do well I can stay in the top 50 and I can play in the Players Championship at Sawgrass next month."

Home favourite Liang, Spain's Larrazabal and Welshman Jamie Donaldson head the chasing pack with American Ryder Cup captain Corey Pavin, former champion Damien McGrane, Peter Lawrie and Korea's Hong Soon-sang a shot further adrift.

Thongchai was in the same flight as the two Ryder Cup captains and Pavin outshone European counterpart Colin Montgomerie with a bogey-free 67.

Scot Montgomerie was forced to settle for a frustrating level par round despite managing six birdies.

Pavin, who finished runner-up at the US PGA Champions Tour event in the Dominican Republic at the end of last month, said: "I was pleased with the way I played. There were no bogeys and that was important for me.

"I played pretty solid and I made a couple of keys putts and hit a lot of good shots and hit a lot of fairways - it was a pretty solid round of golf."

YE Yang, fresh from an eighth place finish at the Masters, was equally in the shadows of countryman Kim and Hong with a 68 leaving the PGA Championship winner rounding out the top 10 alongside world number 16 Henrik Stenson and his fellow Swede Johan Edfors and Finland's Mikko Ilonen, four shots off the pace.