In Samut Sakhon, researchers say, an almost fully preserved whale skeleton believed to be between 3,000 and 5,000 years old has been uncovered.
The bones were discovered about 12 kilometres from the coast in the province just west of Bangkok in early November, the BBC announced on Friday.
The 12-metre-long skeleton is thought to be that of a Bryde’s whale, it said.
Experts hope the find might provide “a window into the past”, especially for research on sea levels and biodiversity.
The partially fossilised bones are “a rare find”, mammal researcher Marcus Chua of the National University of Singapore told the BBC.
“There are few whale subfossils in Asia,” he said, and even fewer ones are “in such good condition”.
Pictures shared by Environment Minister Varawut Silpa-Archa show the bones apparently almost entirely intact.
According to Mr Varawut, more than 80% of the skeleton has so far been recovered, including vertebrae, ribs, fins and one shoulder blade.
The skeleton’s head alone is estimated to be about 3 metres in length.
Mr Chua said the discovery would allow researchers to find out more about the particular species in the past, whether there were any differences compared to today’s Bryde’s whales.
The skeleton will also provide information about the “paleobiological and geological conditions at that time, including sea level estimation, types of sediments, and the contemporary biological communities at that time”.
“So this find provides a window into the past once the skeleton has been dated,” Mr Chua said.
The bones are yet to be carbon-dated to determine their exact age, with the results expected in December.
The Gulf of Thailand has an interesting history in the last 10,000 years, Mr Chua pointed out, with sea levels possibly up to four metres higher than today and active tectonic activity.
Bryde’s whales, which live worldwide in warm temperate and tropical waters, are still found in the waters around Thailand today.