In sweltering conditions at the Dusit Thani Hotel, Keothavong and Cibulkova both struggled to find their rhythm early on, but, aided by a strong serving display, it was the Brit who prevailed, 64 61. After representing Great Britain in the Fed Cup in Israel over the weekend, Keothavong only arrived in Thailand on Monday, but the win - her first over a Top 20 player - will have helped shake off any lingering jet lag. Her reward is a meeting with Sania Mirza, a 36 61 62 victor over Ayumi Morita.
"I didn't have too many expectations going in to today's match as I felt a little under-cooked having only arrived yesterday from Fed Cup in Israel but I surprised myself," Keothavong said. "The courts are super fast here and it's hot and humid. Cibulkova only arrived yesterday too but I think the courts favored my game more and I was quicker to adjust."
There were contrasting fortunes for the three other seeds in the bottom half of the draw; No.3 seed and defending champion Daniela Hantuchova and No.8 Vania King both impressed with straight set wins over Nungnadda Wannasuk and Heather Watson, while No.5 Zheng Jie lost to qualifier Hsieh Su-Wei.
In the top half the No.1 seed and two-time Pattaya champion Vera Zvonareva made it into the second round, although her win over Thai qualifier Varatchaya Wongteanchai was far from routine. In her first match since a surprise third round defeat at the Australian Open, Zvonareva was not at her best, fending off three break points at 5-5 in the second set before eventually closing it out 62 75.
"The first match is always tough," Zvonareva said. "I didn't play my game but I always came up with better shots when I needed them."