Switzerland's world number one Roger Federer defeated compatriot Ivo Heuberger 6-1, 6-3 on Thursday to ease into the quarter-finals of the Thailand Open in Bangkok.

Federer, winner of three Grand Slam titles this year, took the first set in just 20 minutes, conceding one point on serve and allowing his opponent three points in four games after breaking to lead 2-1.

The top seed built a 5-1 lead in the second set before giving up his serve with a double-fault despite holding three match points. But he finally closed out the match with his sixth ace.

"I was happy all the way through. The game I got broken, it's no problem for me to accept that at 5-1," said Federer, who added that Heuberger had been suffering from toothache.

"I was serving well, I was returning especially well. It was tough to play against another Swiss. I'm not used to that, and it was especially hard to keep focused and really close him out."

Russia's Marat Safin beat Jiri Vanek of the Czech Republic 6-3, 6-4 but the third seed needed several match points to reach the quarter-finals.

"I just couldn't finish it for some reason," said Safin. "But I'm not the only player to have these problems. He was trying and didn't miss any opportunities. He had some break points but I served well and he was fighting until the end."

Last year's champion, Taylor Dent of the United States was beaten 6-0, 6-4 by Dutchman Dennis Van Scheppingen.