The decorated Thai, who experienced a sore neck all day, stamped his class when he outshone some of the tournament's marquee names that included world number two Lee Westwood (69) and Rory McIlroy of Northern Ireland (70) to take a share of fifth place at the Sheshan International Golf Club.
"My neck was in a bit of pain as I did not sleep very well last night [Thursday]. I could not turn as much as I would have wanted to. I just had to get my swing shorter and follow it through," said Thongchai.
Starting on the back-nine, Thongchai bogeyed the par-four 11th but recovered quickly with two successive birdies on the 14th and 15th holes to turn in 35.
He moved to three-under after birdies on the third and fourth holes before completing a flawless back-nine with another birdie on the par-three sixth.
"I'm happy that I managed to make birdies on all the tough holes as the greens can be quite difficult on this course. I only missed a couple of short putts. But overall I played very solid today [Thursday]," said Thongchai.
Asian Tour honorary member K.J. Choi also matched Thongchai's opening 68 by mixing seven birdies against three bogeys.
Choi marked his outward-nine by trading two bogeys against three birdies.
After making the turn in 35, the Korean birdied holes two, five and six before another blemish on the par-five eighth dropped him back to three-under.
Choi had a closing birdie on the 18th hole to thank for bringing him back to within three shots back of leader Keegan Bradley of the United States.
"I made several bad tee shots today [Thursday]. In fact I committed all of my bogeys because of all of my poor tee shots. However, my irons from the fairways were good and my putting was also okay," said Choi.
"The key is to allow my body to recover fast and hit my drivers well. But other than that, I believe I stand a good chance," added Choi.