Bangkok - Thailand has sought a clarification from the Indian Navy on its rules of engagement in sinking an alleged pirate ship last week off the coast of Somalia after evidence has emerged that the ship was a Thai vessel, officials said Wednesday.

"We have asked the Indian authorities to help us verify the ownership of the vessel and then clarify their rules of engagement," said Thai Foreign Ministry spokesman Tharit Charungvat.

The Indian Navy frigate INS Tabar sank a suspected pirate vessel November 18 in the Gulf of Aden.

The vessel is now believed to be the Ekawat Nava 5, registered in Kiribati, an island nation in the South Pacific, but owned by Thai national Wicharn Sirichaiekawat.

The Thai Foreign Ministry said it was convinced the "pirate ship" was in fact the Ekawat Nava 5 because the owner of the vessel lost contact with his ship on November
18 while it was in the Gulf of Aden and one of the crewmen, a Cambodian, who survived the attack has provided details of the incident from his hospital bed in Yemen, Tharit said.

According to Wicharn, the ship had a crew of 16 on board when it was attacked, including one Cambodian and 15 Thais. He said the ship was travelling from Oman to Yemen to deliver fishing equipment when it was first attacked by pirates and then attacked by the Indian Navy.

"The ship was raided by pirates, and all of the crew members were tied up when the Indian Navy attacked, according to the survivor," Tharit said.

Thailand has sought a clarification from Indian authorities on whether the Indian Navy frigate attempted to assist any of the survivors after it fired on the vessel and eventually sank it.

"We are still awaiting their answer," Tharit said.

The Indian government said last week that it sank a pirate vessel after it fired on the INS Tabar.

The Tabar had spotted a pirate vessel 285 nautical miles, or 528 kilometres, south-west of Salalah, Oman, and asked the vessel to stop for investigations, it said.

The vessel's response "was that she would blow up the naval warship if it closed in on her," a government statement said.

"Pirates were seen roaming on the upper deck ... with guns and rocket-propelled grenade launchers," it said. "The vessel continued its threatening calls and subsequently fired on INS Tabar."

The Indian warship retaliated, leading to a fire and an explosion on the other vessel. (dpa)