Peter Uihlein overcame illness to record a second round 71 and stay well in the hunt heading into the weekend at the True Thailand Classic Presented by Chang.
The American signed for a 64 on Thursday, which equalled the course record at Black Mountain Golf Club and handed him the 18-hole lead for the second event in a row.
He could not maintain that pace on day two but a birdie-birdie finish got him within three shots of the lead despite the fact he was struggling with the heat in Hua Hin.
"I actually don't feel great – I feel a little bit sick and dizzy," he said. "I think it must be the heat. There is only so much water you can drink but I took some electrolyte powder, had a protein shake and felt a little better but still not great when I was walking.
"This heat certainly tests your stamina. I was saying how much I loved the heat yesterday but today maybe not so much. I'm sure I will be fine – I will load up on carbs tonight.
I am in a good position for the weekend – I am only three back with two rounds to go and that is always a good position to be in going into the weekend - Peter Uihlein
Countryman David Lipsky is also in the group at nine under after he followed his opening 67 with a 68 consisting of five birdies and a single dropped shot.
The 27 year old finished in the top ten last time out at the ISPS HANDA Perth International as part of a sequence of results that has seen him progressively improve his finishing position at every event this season, and he is hopeful of continuing that upward trajectory.
"It is good to see my name up there and to put myself in contention for the weekend," he said. "This is why I play golf – to give myself a chance to win.
"I have been building momentum since the start of the year so hopefully I can keep this form going over the next couple of days."