The unseeded Indian star, who has fallen to 98th in the world rankings from a career-best 27 two years ago, showed no signs of a career-threateneing wrist injury as she battled past 11th seeded Keothavong in the run-up to Wimbledon that begins June 22.
Sania, 22, raced through the first set breaking Keothavong thrice.
The 25-year-old Briton fought back in the second set and seemed poised to level at 5-2.
But Sania successfully defended nine break points that included two set points to enforce a tie-break, which she held her nerve to win closely.
Sania can next run into another Briton, Elena Baltacha.
--IANS