Tammy lost the first set but bounced back to beat American Nicole Gibbs 4-6 6-2 6-1 while Nudnida also needed three sets, beating Japanese qualifier Shuko Aoyama 6-4 2-6 6-2.
The Thai veteran dropped crucial serves in the ninth game which cost her the first set, but she struck back quickly, dropping just three games to win in one hour and forty minutes.
“We had a long rally at four-all and she got a lucky net call on break point. I didn’t serve well and made many errors. But I tried to be more consistent and it worked,’’ said Tammy who next plays top seed Casey Dellacqua of Australia, a 6-2 6-4 winner over Yi-Fan Xu of China.
“I hope that I can raise my level against her. I will have to be solid and offence-minded at the same time,’’ said Tammy, who has beaten Dellacqua on their previous two meetings, at Rolland Garros and Seoul in 2007.
Nudnida, who has improved her fitness and mobility, hit a first-serve percentage that went as high 81 in the decisive set, helping her to win the match in two hours 10 minutes.
“She was consistent and quick. I had to be patient and stay in the rallies. In the second set she opened up the court well and didn’t miss much, so I knew I had to serve well in the third and I did that,’’ said Nudnida, who next plays Samantha Murray of Great Britain, a surprise 6-4 3-6 7-6 (8-6) winner over Japanese second seed Misaki Doi.
In the doubles, Varatchaya Wongteanchai and Miki Miyamura of Japan beat Z Diyas and K Lykina of Kazakhstan 2-6 7-5 10-4 while Thailand’s Noppawan Lertcheewakarn and Aussie Anastasia Rodionova lost to American Chieh Yu-Hsu and Akiko Omae of Japan 6-1 6-2.
In the men’s doubles semi-finals, top seed Sonchat and Sanchai Ratiwatana were upset by Andrea Arnaboldi and Matteo Viola of Italy 6-3 3-6 10-8.