Seiko Okamoto defeated Wing Yau Venise Chan 6-1 6-1 in the Chiang Mai 10K round of 32 on hard. The upset overturned the form book — Wing Yau Venise Chan came in leading the head-to-head 1–0. Seiko Okamoto claimed a first win over Wing Yau Venise Chan in two meetings, narrowing the head-to-head to 1–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2009-07-06 | Shenzhen 10K | R16 | hard | Wing Yau Venise Chan | 6-2 6-3 |
Averages over each player's completed matches in the selected window. ATP, WTA & Challenger.