Seventy-five 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 country's southeastern coast.

Four vessels -- the HTMS Kraburi, HTMS Angthong, HTMS Naresuan and HTMS Bhumibol Adulyadej -- two planes, and four helicopters were scanning the turbulent waters for 30 missing sailors, the navy said.

"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."

The navy had initially reported that 106 people were aboard the vessel, but revised that figure down to 105 on Tuesday.

At the pier in Prachuap Khiri Khan province, families of those missing gathered to wait for news as anxiety over their loved ones mounted.

Malinee Pudpong, 54, from Roi Et province, said her sister's son, 21-year-old Saharat Esa, was onboard.

"I came here to look at the waves and I'm thinking, 'For god's sake, where is my (nephew)?'" she said.

Efforts to find the missing crew were focused on aerial searches, with the Royal Thai airforce assisting the operation, which has been affected by strong winds.

Tuesday's waves were still high, navy spokesperson Admiral Pogkrong Montradpalin said, noting the search area had grown and was focusing "on the area near shores, according to the currents and the wind".

Naval commander Pichai Lorchusakul, speaking at the same pier, said that he remained confident.

"We have full hope," he said.

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

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

Mother Phongsri Suksawat, 50, said she hoped "100 percent" that her 22-year-old youngest son Chirawat Toophorm would come home.

"I thought it would be fine and nothing bad would happen from the storm," she said, adding that before he went on the ship her son asked her to care for his wife.

"I would like to hug him."

- Electrical fault -

Late Monday night, naval commander Pichai 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, adding it was the first time that the Thai navy had lost a ship this way.

The vessel -- a corvette, the smallest type of military warship -- is believed to have run into trouble after its electronics system was damaged, according to the navy.

"The ship's operating systems stopped working, causing the ship to lose control," a spokesperson said.

Parts of southern Thailand have been hit by storms and flooding in recent days.

A warning from the Thai meteorological office remained in place Tuesday, with strong winds causing rough conditions in the Gulf of Thailand, and seafarers cautioned to be careful and small boats to stay ashore.

The HTMS Sukhothai was commissioned in 1987 and built in the United States by the now-defunct Tacoma Boatbuilding Company, according to the US Naval Institute.