Vania King of the United States overcame the Czech Republic fourth seed Lucie Safarova 6-1, 6-1 to move into the quarter final of the Bangkok Open on Thursday.
The 17-year-old American will face left-handed Croatian Jelena Kostanic, who scored a comfortable win over Marta Domachowska of Poland 6-1, 6-0.
King, who is looking for her first WTA title, started the game well and gave few chances to Safarova, who made repeated unforced errors during 59 minutes of the match time.
"I feel pretty good about today's match, actually I feel really good about it. I respect her, but she wasn't at her best today, she never seemed to find her rhythm," King told reporters.
Austrian Sybille Bammer caused a big upset by defeating France's Nathalie Dechy, the third seed and world number 39, in two straight sets 6-3, 6-1 to reach the quarter final.
Bammer, who is ranked 56 in the world, played solidly from the outset, making few unforced errors, while Dechy could not control her game.
The Austrian took a 3-0 lead and Dechy closed it to 3-2, before Bammer broke the French woman's serve, finishing the first set 6-3, and later sealing her victory with backhand winner for 6-1 in the second set.
"I play really well here in Thailand because I love the heat." said Bammer, who reached the semi-final in the Pattaya Open earlier this year.
"I was expecting the match to be tougher," she added.
Croatia's Jelena Kostanic needed just 56 minutes to overwhelm Poland's Marta Domachowska. Kostanic allowed Domachowska only one game in the first set as the tournament eighth seed took the match at 6-1, 6-0.
Greece's Eleni Daniilidou made it through to the quarter finals by defeating Japan's Erika Takeo 6-4, 6-4.
Thailand's number one, Tamarine Tanasugarn, also reached the quarter finals with a victory over Jamea Jackson of the US, who retired due to hamstring injury at 6-1, 2-0.
"Today I am lucky to win the match but very unlucky for her as she has an injury today," said Tamarine.
Tamarine will next play left-handed player Bammer for a place in semi-final.