Stark went around the second round of 67 shots, five under par after five birdies.
She is second for the second day in a row.
- It was very steady.
I only needed to save a single pair, says Stark according to the AP.
Anna Nordqvist shared the lead after Thursday's first round but slipped down the leaderboard, to eighth place, three strokes behind the lead.
Frida Kinnhult also shares eighth place after completing the round of 68 strokes and is in the fight for victory.
Home player Natthakritta Vongtaveelap is the new leader after 65 strokes, seven under par, in the second round.