A Thai couple were delighted after finding a lump of valuable whale vomit on a beach - which could be worth up to $600,000.

Veera Juengboon, 31 and his wife Monruedee, 26, travelled to Phuket, southern Thailand to see a friend when they went noticed the lump during a romantic beach walk.

The yellowish mass was covered in a pile of trash that washed up on the beach last month.

However, Veera, who likes watching science documentaries, recognised the precious substance from shows he had seen before. It resembled ambergris, a rare secretion from whales that floats in the ocean - often for decades - and can be used as an expensive ingredient in perfume.

The excited husband told his wife about it and they carried the 15kg rock back to their hotel room, where they started examining it.

Veera lit a small part of the mass using a lighter which melted quickly, suggesting it was ambergris. They also checked its appearance - soft, smooth, and waxy - which made their hopes even higher.

The couple almost sold the rare substance through social media, but they decided to keep it in the meantime.

When news emerged last month that a fisherman in Nakhon Si Thammarat had found a similar item, the couple decided that they would look for a buyer.

Veera this week on Monday (Dec 21) called reporters to announce they had found a piece of ambergris and that they are ready to sell it.

He said: ''One person contacted me when we posted a video of the rock social media. They asked if they could buy it but we said no.

''I feel very lucky to have discovered the whale ambergris. I've tested it a few times and I'm sure it's real.''

The ambergris could be worth as much as $40,000 per kg, depending on the quality. That would net the couple the equivalent of around $600,000.

The heavy mass of ambergris still does not have a buyer, but the couple said they are now willing to accept offers.

Ambergris is produced by sperm whales when their bile ducts in the gastrointestinal tract make secretions to ease the passage of large or sharp objects. The whale then vomits the mucilage which solidifies and has a foul smell as it floats across the ocean surface - sometimes for several years.

Despite the unappealing smell and appearance, when the mucilage dries out the chunk takes on a beautifully sweet scent and long-lasting aroma, which makes it a sought-after ingredient in the perfume fragrance industry.

In April 2016, a 1.57 kilogram ambergris ball found in Lancashire sold for GBP50,000 while in November of the same year, three Omani fishermen found 80 kilograms of ambergris and sold it for USD3 million.