Sixth seed Meghann Shaughnessy cruised past India's Sania Mirza 6-4 6-4 on Tuesday to reach the second round of the Bangkok Open, just before rain washed out the afternoon schedule.
"It's always difficult when the weather delays things," the American told reporters. "I came out quite aggressive. I played well. She's a good player and when you know you're down to face her, you're always on edge."
A below-par Mirza later withdrew from her first round doubles match with stomach problems.
Germany's Julia Schruff beat Emma Laine of Finland 6-4, 7-6 to go through while Sybille Bammer of Austria saw off Australia's Nicole Pratt 6-1, 6-3.
Home player Tammarine Tanasugarn returned after a three-hour break to beat Colombia's Catalina Castano 6-0, 7-6.
The Thai regained her focus to finish off a second set tiebreak in just seven minutes to advance to the second round.