Manassero became the youngest ever winner of the BMW PGA Championship in 2013, claiming his fourth European Tour title at the age of 20 in a play-off at Wentworth.
The 22-year-old Italian has recorded just three top-10 finishes since then and missed the cut in his first five events this season, but a second round of 68 at Tomson Shanghai Pudong Golf Club gave him a share of the clubhouse lead with Aphibarnrat on five under par.
“I’m playing very solid golf and I’m glad to have my confidence back and to be shooting some good scores again,” Manassero said. “I like this course and it suits my game.
“I struggled on the greens last week and I missed some shots to the right, which you couldn’t afford to do on that course. But this week I’m hitting it much straighter and I’m reading the greens much better, which is why I’m much nearer the top of the leaderboard.
“It’s now much less complicated for me to work through my process. And because I’m hitting it straighter and shooting lower scores, that obviously that leads to your confidence coming back.
“I’m not there yet and I don’t want to say I’m completely out of the woods just yet, but everything is much clearer now and I’m on a much better path.”
Aphibarnrat, who won the Shenzhen International in a play-off on Sunday, also added a 68 to his opening 71 thanks to five birdies and one bogey.
“I’m very happy, especially as it’s playing tough – there are lots of slopes on the greens and the course is very firm,” the 25-year-old Thai said.
“I’m not driving the ball as well as I did last week, but the rest of my game is in pretty good shape, especially my short game.
“I’m still feeling good; I’ve been getting lots of rest and eating well, so I’m feeling fine and ready to go. Mentally I’m still sharp and my confidence is high, so I just have to keep it up.
“My mum is still here with me and she told me to keep going and win back to back, so hopefully I can do it for her. She’s my good luck charm.”
France’s Julien Quesne had moved into the lead out on the course, four birdies on the front nine taking him to seven under par and a shot ahead of compatriot Alexander Levy.
Levy, the defending champion, had picked up shots on the second, fifth and seventh.
Joint overnight leader Bradley Dredge was five under par after nine holes of his round, with David Howell on four under after only managing to add a 72 to his opening 68.