Defending champion Jo-Wilfried Tsonga needed three sets to beat Ernests Gulbis to reach the quarter-finals of the Thailand Open.

Top-seeded Tsonga took two hours and 12 minutes to see off the Latvian 6-7 (3/7) 7-6 (7/4) 7-6 (7-2).

Second seed Gilles Simon made lighter work of his second round tie, cruising past Kevin Kim 6-2 6-2 in just 61 minutes.

Simon will meet Evgeny Korolev after the Russian crushed Robby Ginepri 6-1 6-1.

Retiring former world number one Marat Safin limped out of the tournament.

The Russian, who intends to retire at the end of the year, was dismissed by Swiss qualifier Marco Chiudinelli 6-3 7-6 (7/4).

Eighth-seeded John Isner ensured his progression with a 7-6 (7/5) 6-4 triumph over German Mischa Zverev

Elsewhere, Andreas Beck was forced to work hard before defeating Donald Young 6-1 6-7 (7/3) 6-4.