PATTAYA CITY, Thailand - Fifth-seeded Peng Shuai, the only seed in action on the first day of the PTT Pattaya Open, narrowly escaped the upset bid of Italy's Mara Santangelo on Monday.

After dropping the first set 6-3, the 23-year-old from China was up 5-2 in the second when Santangelo had to retire due to a stomach illness. Earlier in the match, she had to be treated for a left ankle sprain. Peng, who fell to eventual champion Serena Williams in the third round of the Australian Open, will next play Kazakhstan's Galina Voskoboeva, a 46 62 61 winner over Jarmila Groth. If she gets through that, a possible match-up with top-seeded Vera Zvonareva looms in the quarters. Peng, currently ranked No.35 in the world, reached the semifinals in 2007 in her only previous appearance in Pattaya City.

In the only other main draw matches of the day, Vera Dushevina topped Elena Bovina 64 75 in an all-Russian affair and another Russian, Ksenia Pervak, beat Japan's Tomoko Yonemura, 61 61.

Sesil Karatantcheva, Vitalia Diatchenko, Yuliya Beygelzimer and Ivana Lisjak all secured main draw berths with wins in the final round of qualifying.

Australian Open mixed doubles champ Sania Mirza, No.2 seed Caroline Wozniacki and Zvonareva headline Tuesday's schedule. Also, fourth-seeded Sybille Bammer of Austria has an intriguing match against Polish 18-year-old Urszula Radwanska, the sister of last year's champion, Agnieszka Radwanska, who is playing in Paris this week.