World number five Thiem needed one hour and 46 minutes to secure a 7-5 6-4 victory over Aljaz Bedene in a match in which he had 15 break-point chances, taking just three of them.

The Austrian recognises he could have been more clinical, but was delighted to reach the last eight.

"The first set was good, I converted break points fine," Thiem said. 

"But second set I think I missed too many chances. In general I'm very happy."

Thiem's chances in Qatar were heavily improved by the exit of several top seeds on Tuesday, and Richard Gasquet (5), Fernando Verdasco (7) and Feliciano Lopez (8) added to the list of casualties in round two a day later.

Gasquet could have set up a clash with Thiem but was upset by world number 91 Stefanos Tsitsipas 6-3 6-4.

Lopez was a 6-4 7-6 (7-2) loser against qualifier Mirza Basic, while his fellow Spaniard Verdasco bit the dust in a 6-4 3-6 6-4 loss to Andrey Rublev.

Borna Coric, who accounted for second seed Pablo Carreno Busta 24 hours earlier, overcame Nikoloz Basilashvili 6-1 6-3, wildcard Gael Monfils needed three sets to defeat Jan-Lennard Struff, and there were also wins for Guido Pella and Peter Gojowczyk.