Pattaya City, Thailand (SportsNetwork.com) - Top seed Peng Shuai suffered a second-round upset Wednesday at the Thailand Open.

Japan's Misaki Doi knocked out the Chinese Peng in 6-3, 2-6, 6-2 fashion at this hardcourt event.

"She's a very strong player," Doi said after the match. "She's No. 1 seed, so it was always going to be difficult for me, but I just tried to go out and enjoy the match and luckily I played well."

In other action involving seeds, No. 7 Monica Puig of Puerto Rico snuck past Swiss Romina Oprandi 6-1, 3-6, 6-0 and Russian wild card Vera Zvonareva tackled No. 8 Chinese Zhang Shuai 7-6 (8-6), 6-3.

"I felt pretty good. It was a very tough match and we had a very close first set," Zvonareva said after besting Zhang. "She's a very good player and has had some great results over the past three years while I was away. It was a great opportunity for me to test myself and I'm very pleased with how I played and that I fought very hard."

Puig will face the 104th-ranked Doi in the quarterfinals, while Zvonareva will take on New Zealand's Marina Erakovic, who mauled Ukrainian lucky loser Yuliya Beygelzimer 6-1, 6-1.

The two-time Grand Slam runner-up and former top-10 star Zvonareva is a two- time Pattaya City champion. She's still on the mend following a shoulder injury.

The 2015 Thailand Open titlist will claim $43,000.