The Swiss world number one said a quarter-final battle against Sandrine Testud of France less than 24 hours before had left her drained.

"I was still a little bit tired from yesterday and couldn't somehow get it going," said Hingis who will face either third seed Nathalie Tauziat of France or Australian qualifier Rachel McQuillan in the final.

"I was also a little bit dizzy on the court and I felt not really out there. Maybe it's because I lost a lot of fluids last night.

"I've also played a lot of tennis over the past few weeks and sometimes mentally you get a little bit tired going out there match after match."

Tanasugarn served for the set at 5-4 and held three set points, but Hingis saved the first with a fine service return, the second with a well-controlled overhead, and was gifted the third when Tanasugarn netted a backhand.

In the tiebreaker, Hingis fluffed her first set point by double-faulting at 6-5, but she took the 59-minute set when Tanasugarn again netted a backhand at 7-6.

Hingis said: "Sometimes you pull things out and you don't know how. Yesterday I should have lost, and the same today maybe I should have lost the first set.

"I didn't like her serve too much, and then she started only serving second serves and I could attack, especially in the second set."