Mirza trailed 5-3 in both sets against the 945th-ranked Nicha.
"She didn't play like she is 945. She hit like she is in the top 50,'' Mirza said. "It's always difficult to play with someone you don't know in the first round. But I'm happy to raise my level and pulled through.''
Top-seeded Vera Zvonareva of Russia also advanced, beating Andreja Klepac of Slovenia 6-4, 6-3, while second-seeded Caroline Wozniacki of Denmark defeated Chan Yung-jan of Taiwan 6-3, 6-0.
Also, fourth-seeded Sybille Bammer of Austria, the 2007 champion, beat Urszula Radwanska of Poland 6-4, 3-6, 6-1; Yuliya Beygelzimer of Ukraine beat Anastasia Rodionova of Russia 6-2, 6-2; Neuza Silva of Portugal defeated Jessica More of Australia 6-2, 6-1; Yaroslava Shedova of Kazakhstan eliminated Tamira Paszek of Austria 6-3, 6-4; and Ivana Lisjak of Croatia beat Bulgarian qualifier Sesil Karatancheva 6-2, 4-6, 6-3.
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