BANGKOK (AFP) - Two-time winner Tseng Ya-ni hit seven birdies on Thursday to share the overnight lead with American duo Stacy Lewis and Brittany Lang after the first round of the Honda LPGA Thailand.

It might have been even better than six-under 66 for the Taiwanese golfer but for a dropped shot on the final hole that tarnished an otherwise perfect round at the Siam Country Club.

Nonetheless it left Tseng - who won in Thailand in 2011 and 2012 - in the unfamiliar territory of leading after the first round in a tournament for the first time in three years.

World No. 3 Lewis came out blazing, notching an eagle on the par-five first, followed by five birdies to go round the front nine in a stunning 29. But she drifted in the back nine, dropping two shots to finish on 66.

Compatriot Lang had an indifferent start to the day, bogeying No. 6 before rattling off five birdies in a row and eight in total.

The trio are just a shot ahead of a strong field boasting four top-10 players. Home favourite Ariya Jutanugarn, who was edged into second place in the nail-biting 2013 edition, was among six poised a shot behind on 67, including world No. 6 Suzann Pettersen, who hit an error-free six under par.

World No.2 Park Inbee finished on a two-under 70 for the day, after an error-strewn round which saw her drop four shots.