By Rattabhum Ninsiri
BANGKOK (Reuters) - World number one Rafa Nadal advanced to the semi-finals of the Thailand Open with a 6-2 6-3 win over Kazakhstan's Mikhail Kukushkin on Friday.
The Spaniard, who won his ninth grand slam at last month's U.S. Open, overpowered the 22-year-old with a polished all-round performance.
Nadal broke the 83-ranked Kazakh at 3-2 in the first set and won six straight games before Kukushkin answered back. Nadal served well throughout the second set and kept his opponent on the back foot with some punishing forehand drives.
"It was a much better performance than yesterday and I felt really happy. My serve-kick worked really well," Nadal told reporters.
Referring to his U.S. Open triumph, Nadal said he still had more room for improvement and admitted it would be difficult to keep his number one ranking for a long time.
"I'm not the best tennis player yet. Winning and losing depends on how I prioritize. I just want to enjoy it and become a better player year by year," he added.
Unseeded Jarkko Nieminen and Benjamin Becker booked places in the semi-finals after impressive runs in a tournament decimated by early exits of its top-ranked players.
Finland's Nieminen beat third-seeded Austrian Juergen Melzer 6-3 7-6 to set up a semi-final with Becker, the 2007 finalist, who outplayed fellow German Daniel Brands 6-4 6-2.
Nieminen, the world number 60, put his form down to a recent change in coach and improvements to a game he said had stagnated.
"We've worked on a lot of things, especially the serve, and everything takes time to take shape," he told reporters.
"I'm 29 now and I have been doing the same things for a long time, so it takes a while to implement changes into my game but I think I am serving better than ever now."
Nadal and Latvian Ernests Gulbis are the only seeded players left in the competition. Gulbis was due to play Spain's Guillermo Garcia-Lopez later on Friday.
Those who made early exits include second-seeded Fernando Verdasco, former U.S. Open champion Juan Martin del Potro and Serbian Viktor Troicki.
(Writing by Martin Petty; Editing by Justin Palmer)