District Chief Officer Sermsak Seesan of Thailand's northern Chiang Rai's Chiang Saen told Xinhua on Monday that he and other Thai authorities were ready and willing to help Chinese officials in the investigation over the hijacked ships and protection of Chinese ships.

Thai authorities will cooperate with Chinese and Laos officers to protect commercial ships plying Mekong River in the future, said the chief officer, who is also the head of the investigation team.

According to Sermsak, Thai police, relevant authorities, military together with Chinese police officers from Sipsongbanna ( Xishaungbanna) Prefecture and the media investigated the two ships again Monday morning. They found many bullet holes from M16 assault rifles and 9MM caliber scattered inside the ships.

Sermsak unveiled that the investigation team believed the gang hijacked the ships to demand for protection money and killed all the crews to keep their mouth shut.

The investigation team believed that the Tai Yai ethnic group, or Shan, drug trafficking gang led by Nor Kham was behind the attack as his gang is normally active in the areas along the border of Golden Triangle.

Last Wednesday, Thai Pha Meung Task Force border troops captured two Chinese-flagged ships coded Yi Xing 8 Hao and Hua Ping and seized some 951,000 pills of methamphetamine on board after a gunfight of about half an hour with drug traffickers, in Chiang Saen District, bordering Myanmar. One drug trafficker was reported to have been killed.

Thai authorities on Monday confirmed all the 13 Chinese crewmen on the two hijacked ships were killed.

According to Thai military, Nor Kham, wanted on Thai and Myanmar arrest warrants for drugs trafficking, had expanded his illegal activities to collect protection money from Chinese- flagged cargo ships a few years ago.