Former Wimbledon champion and sixth seed Petra Kvitova was embarrassed by little-known Thai Luksika Kumkhum Monday, who sent her packing from the Australian Open in the first round.
The Czech came into the tournament in decent form after making the final of the Sydney International, although she fell to Bulgarian qualifier Tsvetana Pironkova.
And she had chances against Kumkhum, ranked 87 in the world and facing a top 10 player for the first time, but failed to show the killer instinct that took her to the Wimbledon title in 2011.
Her 6-2, 1-6, 6-4 defeat made her the highest seeded casualty so far.
For Kumkhum, backed by a noisy crowd, it was the biggest victory of her career and was all the more remarkable after she failed to get through qualifying at the Shenzhen Open and Sydney tournaments in the lead-up to Melbourne.
"I'm very excited to beat the number six player in the world," she said. "Today is a great day for me, I am very happy."
The Thai number one, whose best tournament performance was reaching the quarter-finals in Kuala Lumpur last year, will now face Germany's Mona Barthel who beat China's Zhang Shuai.