Bangkok: 2009 Thailand Open winner Gilles Simon of France continued to struggle with shoulder problems but managed a 6-4, 6-4 defeat of Japan's Go Soeda on Thursday to reach the quarter-finals.
Simon will line up for a semi-final spot on Friday when he faces compatriot Gael Monfils, playing in only his second event since returning after four months away with a knee injury.
Monfils upset Serb sixth seed Viktor Troicki 7-5, 7-5, changing tactics after trailing in the opening set.
"He was playing better early on and I was giving him mistakes. I tried a lot of things," said the former French Open semi-finalist. "Finally I began slicing more and hitting harder, it turned into a physical fight, I was able to run him all over the court.
"I'm gaining confidence from another quality win here. It was my second tough match here."
Monfils said that while he does not doubt Simon's complaints about shoulder problems, he noted that his compatriot has not forsaken any ATP play as a result.
"How many events has he missed? Four months out with a knee injury is much worse. I'd much rather be him than me going into our match. I'm not saying he has nothing (wrong), but he's still been playing all along."
Simon won the first two matches with Monfils, with his rival claiming their last one in February indoors at Montpellier.
Australian Bernard Tomic, seeded eighth, struggled in his own way as he played a tennis replica of himself, coming out a 4-6, 6-3, 6-4 second-round winner over Israeli opponent Dudi Sela after nearly two and a half hours.
Spanish fifth seed Fernando Verdasco put out 2011 finalist Donald Young 7-5, 6-4.
Tomic, whose own game gives opponents no chance to find their rhythm, found he was facing a mirror image of himself -- and the 19-year-old admitted that he didn't like it one bit.
"It was difficult to play aggressive against him, he gives you all kinds of stuff -- like I do. I guess that's why guys don't like to play me.
"He gives you a lot of low balls that I don't like. It was tight in the second and third sets, I was too defensive in the first set, but he doesn't give you the chance to play aggressive with his style.
"It was tough for me, he's been around and is tough to play," said Tomic, who has now reached the quarter-finals in just four of his 22 tournaments in 2012.
The Aussie, who is ranked 41st and the only teenager in the ATP top 50, will play for the semi-finals against either French second seed Richard Gasquet or Grigor Dimitrov.
Simon said that his long, slow recovery form a shoulder injury is still taking a toll on his game as he faced Soeda, a 2011 Bangkok quarter-finalist.
"I'm not serving my best and that makes life difficult," said the 19th-ranked Simon. "I don't get any easy points, I have to fight every point from the baseline.
"I think we played a great match, all things considered. I had to play incredible from the baseline, I'm just happy to get through this one. My shoulder is slowly getting better, but I must continue to play this way for now."