The Idemitsu Honda Team Asia rider started from poll position for the first time in his career but fell victim to a rain-slicked track in the northeastern province.
Thai fans were left shocked when their home hero lost grip on the fourth bend while leading the race and slammed his bike heavily down onto the tarmac. Medics rushed to the scene before sending Somkiat to hospital with an arm injury.
Italy’s Tony Arbolino (Elf Marc VDS) crossed the finish line in first place after the race was shortened following another heavy downpour. Felix Salac of Czech Republic was second while Spaniard Aron Canet took third. Championship leaders Ai Ogura and Augusto Fernandez were sixth and seventh respectively.
Somkiat earlier snatched Thailand’s first-ever Grand Prix pole position on Saturday with a qualifying time of 1 minute and 35.625 seconds.
He started Sunday’s race ninth in the Moto2 championship on 120 points.