Like her previous two matches, Napaporn came from a set down to upset American fifth-seed Sunitha Rao 3-6 6-3 6-2 to reach her third semi-final at the challenger level this year.

"I lost the first sets in the first and second rounds and came back to win. So I was thinking I should be able to pull it off again in this match," said the Thai No 3, who had previously reached semi-finals in China and South Korea.

American-Indian Rao was the second seeded victim for the Thai, who knocked out No 2 seed Vilmarie Caste-llvi of Puerto Rico in the first round.

"I don't know what's wrong but I've always struggled to find my momentum in the first sets for three days. But I never put pressure on myself, even when I was behind. In fact, it was my opponent who was tense," said Napaporn.

After losing the first set, Napaporn went on the attack, while Rao concentrated on defence. The Thai then started to dominate the match.

"She was obviously afraid I would get back into the match as she turned a bit stiff. I saw that opportunity to attack her," said the Thai.

In the semi-finals Napaporn will meet Tatiana Perebiynis of Ukraine, the fourth-seed who moved past Japan's Mari Tanaka 6-2 6-2. The 194th ranked Ukrainian is a former top 100 player whose ranking peaked at No 73 in 2004.

"It's going to be the toughest match in this tournament for me. She has good groundstrokes and hardly misses," said Napaporn.

Meanwhile in Bangkok, Varatchaya Wongteanchai and Nungnadda Wannasuk won the doubles after their 6-4 6-4 victory over Kai-Chen Chang of Taiwan and Thuy-Dung Nguyen of Vietnam in the US$10,000 PTT Bangkok Open Circuit 1 tournament at the Rama Gardens Hotel yesterday.