BANGKOK — Defending champion Jo-Wilfried Tsonga of France beat Switzerland’s Marco Chiudinelli 6-7 (7), 6-3, 6-4 to reach the semifinals of the Thailand Open today.

Ranked No. 7 in the world, the top-seeded Tsonga recovered from a brief bout of nerves in the first set tiebreaker, serving 20 aces to overcome Chiudinelli, ranked more than 100 places below him.
“It was a difficult match for me,” Tsonga said. “Marco played well like (Ernests) Gulbis did against me yesterday. But it was good for me to have these tough matches to gain my confidence. It’s important for me to have a victory.”
Tsonga was taken to three tiebreakers before defeating Latvian Gulbis in the second round.
Tsonga will play the winner of the quarterfinal between fourth-seeded Viktor Troicki of Serbia and eighth-seeded John Isner of the United States.
Earlier Friday, second-seeded Gilles Simon of France reached the semifinals by beating big-hitting Evgeny Korolev of Russia 4-6, 6-3, 6-4.
Simon struggled to counter the 66th-ranked Korolev’s groundstrokes in the first set, having to chase down shot after shot before finally starting to force some errors.
“He played amazing tennis in the first two sets,” the 10th-ranked Simon said. “He rarely gave me any chance in the first set, and hit the ball really hard.”
Simon will next play sixth-seeded Jurgen Melzer of Austria, who defeated Germany’s Andreas Beck 6-4, 6-2.
“Melzer is a good player,” Simon said. “I saw him play. He didn’t miss for the whole match. He is good in every part of the game. I expect a hard match.”
The 44th-ranked Melzer reached his second semifinal of the year after making the final four in Umag, Croatia, in June.
“It looked easy but it was not easy,” he said. “I played a really good match. I put a lot of pressure on him with my serves.”