BANGKOK (AFP) - Defending champion Amy Yang finished with a one shot lead on Friday in day two of the Honda LPGA in Thailand.

The South Korean spent the day jockeying for the top of the leaderboard with first round front-runner American Lexi Thompson, who dropped down to second during round two at the Siam Country Club in Chonburi.

While her rivals dropped shots on the inward nine, Yang finished in front posting 69 at three under par for the day and totalling 135 at nine under par.

"I mean, I struggled a little bit on the front, two bogeys straight, but I think I stayed patient well, got through it well," Yang said, according to an LPGA statement.

"I'm happy with today's round," she added.

After a strong start on day one Thompson fell behind on Friday as the greens firmed up, ending the round with a 136 total at eight under par alongside fellow American Jessica Korda and South Korean starlet Q Baek.

If Yang defends her title on Sunday she will be the event's second back-to-back winner in the Honda LPGA's 10-year history.