The executions were carried out by lethal injection by a court in Kunming, capital of the south-western border province of Yunnan, state media quoted local officials as saying.
Thai citizen Hsang Kham, Lao citizen Zha Xika, and Yi Lai, who was stateless, were executed along with Nor Kham after the nation's highest court approved their death sentences.
In an unusual move, Chinese authorities allowed state media to film and photograph Nor Kham during his transfer early Friday afternoon from a detention centre to the court's execution area.
State broadcaster China Central Television showed police removing Nor Kham's handcuffs and binding his arms behind his back with rope, a standard ritual before executions in China.
Earlier reports said the court had arranged for relatives and representatives of the Thai and Lao consulates to meet the men in Kunming before their executions.
Nor Kham and his gang were found guilty of attacking two Chinese cargo ships in collusion with Thai soldiers, while they kidnapped other Chinese sailors and held their ships for ransom earlier in2011, the court said.
At his appeal hearing in December, Nor Kham was quoted as saying he "neither plotted nor ordered the murder" of the sailors in October2011 and only heard about the attack later.
During his trial, Nor Kham accused Thai soldiers of sole responsibility for the attack.
But he later pleaded guilty to the charges, before changing his plea again at the appeal hearing, according to state media reports.
Two other members of Nor Kham's gang, both Myanmar citizens, were given a suspended death sentence and eight years in prison for their involvement in the murder, kidnapping and hijacking.