BANGKOK (AFP) - On a day in which the oppressive heat sapped the strength of even the strongest players, Jamie Donaldson held on to a two-shot lead in the second round of the Thailand Golf Championship at Amata Spring Golf and Country Club on Friday.

The Welsh Ryder Cup star fired a four-under 68 to total 131 and keep two clear of a charging Martin Kaymer who moved into second spot with an excellent 65, the best round of the day.

Spain's Sergio Garcia, who shot 69, led the chasing pack a further two strokes behind, along with the impressive English youngster Matthew Fitzpatrick who shot an excellent 67 and Thailand's Chinnarat Phadungsil with a 69.

In joint sixth place on 136 were South Korea's Byeong Hun An with a 67 and Thailand's Panuphol Pittayarat who shot 66.

Donaldson, who fired a magnificent 63 in the opening round, admitted the tropical heat was a factor.

"It was a great temperature to start with, but it got really hot on the back nine," he said. "It was tough out there and a case of trying to stay hydrated and not drop sweat on the ball."

Kaymer also had problems with the heat, although it did not seem to affect his play. "It was like a sauna out there," he said. "They say you get nicer weather in the morning, but that was not really the case today. But the good thing is that the ball goes further."