Former champion Gilles Simon battled a back injury and jetlag to book his spot in the semi-finals of the Thailand Open with a tough three-set win on Friday over Dutchman Igor Sijsling.

Simon, seeded fourth and winner of the Bangkok event in 2009, called for the trainer after the opening game of the final set, but recovered to take the game and continue a strong run of form.

The Frenchman, who is ranked 14th in the world, came to Thailand on the back of taking the title in Metz last weekend, where he beat compatriot Jo-Wilfried Tsonga, and has been fighting jetlag all week.

Despite early starts in the Thai capital, he notched his 300th career win on Thursday over Australian Bernard Tomic 6-4 7-5.

Simon, who lost to compatriot Richard Gasquet last year in Bangkok, will bid to reach his third Thailand final when he plays top seed Tomas Berdych or Lu Yen-Hsun of Taiwan, who are on court later on Friday.

Simon claimed victory 6-4 5-7 6-4 in just under two-and-a-half hours with his eighth ace of the match after saving a slew of break points from the attacking Sijsling.

The Frenchman won the opening set in 54 minutes, prevailing in a battle of classy groundstrokes between the two men.

Sijsling rallied to claim the second set and looked to be in control early in the third when Simon was forced to take his on-court treatment.

But Simon regained his composure with a break for 4-3 and took victory three games later on his second match point.