PRACHUAP KHIRI KHAN, Thailand (AFP) — The Thai navy said it rescued one sailor on Tuesday, nearly two days after a military vessel sank, with 29 still missing at sea.

"We have found someone during daytime today," naval commander Pichai Lorchusakul said, adding the man was in "good health."

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 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," naval officer Narong Khumburi said.

"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 and his 176-strong crew is joining 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.