Ratthapark Wilairot is to retire from grand prix racing with immediate effect.

The Thai star, just 25, will be replaced at the Gresini Suter Moto2 team by rookie countryman Thitipong Warokorn, whom Wilairot will help to coach.

Wilairot made his grand prix debut as a wild-card in the 250cc class back in 2006, starting his first full World Championship season the following year.

Thailand's first grand prix rider raced exclusively in the intermediate class, with a best championship ranking of 13th in both 2008 and 2009.

The four-stroke Moto2 era began promisingly when Wilairot claimed what would be career best fourth place - less than a tenth of a second from the podium - on a Bimota chassis at Assen, although he concluded the year 22nd overall.

But Wilairot suffered serious injuries in a road accident prior to 2011, then further injuries late that year when he was struck by Marc Marquez after the chequered flag had been waved during practice at Phillip Island, an incident the Spaniard was penalised for.

Aided by his loyal Honda and PTT backing, Wilairot switched to the Gresini team for 2012, but was left 27th in the standings and - like Indonesian team-mate Doni Tata Pradita - has not scored a point in 2013.