Top seed and holder Jo-Wilfried Tsonga advanced to the semi-finals of the Thailand Open after a testing 6-7, 6-3, 6-4 win over unseeded Swiss Marco Chiudinelli on Friday.
The French world number seven, who squeezed through in a tense opening match a day earlier, recovered after losing a first-set tiebreak to plot his course for the semis, where he will meet Viktor Troicki or John Isner.
Second seed Gilles Simon advanced in the $608,500 tournament after fighting the pain barrier to record a 4-6, 6-3, 6-4 victory over hard-hitting Russian Evgeny Korolev.
The Frenchman held his nerve in a battle of back-court slugging, capitalising on a flurry of errors by Korolev to reach the last four for the third time this year.
Korolev blasted his way through the first set but was later drawn into a succession of unforced errors by the world number 10, who was carrying a knee injury and was content to play defensively for most of the match.
"It was hard to play him," Simon told reporters. "He hit the ball really hard. Finally my plan was to hold my serves and wait for his mistakes."
Simon will meet sixth-seeded Austrian Juergen Melzer after he overpowered German Andreas Beck in a 6-4, 6-2 win.