BANGKOK, April 8 (Reuters) - The three crewmen on the Thai-flagged vessel that was attacked in the Strait of Hormuz last month have died, Foreign Minister Sihasak Phuangketkeow said at a press conference on Wednesday. 

Thailand said 20 crew members were rescued by the Omani navy after the attack, which caused an explosion in the stern of the ship and a fire in the engine room.

Sihasak said he would travel to Oman in mid-April to seek assistance in coordinating with Iran to secure safe passage for nine Thai ships that are still stranded in the Strait of Hormuz.

A Thai oil tanker travelled safely through the waterway late last month and was not required to pay to escape the blockade. 

(Reporting by Chayut Setboonsarng, Editing by David Stanway)