BANGKOK, Dec 20 (AFP) - Rescuers in helicopters scoured the Gulf of Thailand on Tuesday for dozens of sailors who went missing when their naval vessel sank, hoping life jackets had helped them survive two nights in the choppy waters.

Seventy-six sailors from the HTMS Sukhothai were hauled from the sea after the vessel went down late Sunday in the Gulf of Thailand, roughly 37 kilometres (22 miles) off the Southeast Asian country's southeastern coast.

Thai warship the HTMS Kraburi left port to resume the search early Tuesday, scanning the turbulent waters for 30 missing sailors alongside other naval vessels and two Seahawk helicopters.

"I am hopeful we will find some survivors, because they have life vests," said naval officer Narong Khumburi.

"But I imagine they must be exhausted."

Efforts to find the missing crew were focused on aerial searches, with the Royal Thai airforce assisting the operation.

HTMS Kraburi commander Kraiwit Kornraweeprapapitch said slightly improved weather would help the search.

"The format of searching is still the same, which is a joint operation with helicopters," he said.

His ship and 176-strong crew will join the HTMS Angthong, HTMS Naresuan and HTMS Bhumibol Adulyadej in scanning an area roughly 30 miles by 30 miles stretching from Prachuab to upper Chumporn.

"Now, we are just surveilling the situation using the helicopter," naval diver Prawit Gongnak told AFP at the pier in Prachuap Khiri Khan town.

Prawit, who was monitoring the bright if blustery weather conditions, said he was among 29 divers on standby.

"We haven't been commanded to dive yet," he added.

Sahachart Limcharoenphakdee, a member of the National Institute for Emergency Medicine, said they were working with naval personnel to help those plucked from the waters.

"I am hopeful, and have trust for the navy rescue team who are skilful," he said.

Late Monday night, naval commander Pichai Lorchusakul told reporters at the pier that they remained focused on finding survivors.

"Our main priority is searching (for) and rescuing as many as we can," he said.

Pichai added that this was the "first time" that the Thai navy had lost a ship this way.