Shocking footage shows emaciated horses that were found at an equestrian centre on an island in southern Thailand.

A tourist who looked up the school on Google was hoping to go on a horseback trek - but when she arrived instead found dozens of dying ponies at the riding school on Koh Samui in Surat Thani province.

Many had collapsed on the ground and starved to death.

Concerned by the state the horses were in, the backpacker reported the case to the non-profit charity Watchdog Thailand Foundation (WDT) on December 23.

The organisation took heartbreaking photos and videos showing the skeletal horses lying on the ground with their ribcages visible and patches of hair missing.

Some of the horses were unable to stand, their legs buckling due to hunger and exhaustion.

The animal charity claimed several of the horses had already died of starvation, as they were left with no food or suitable grasslands to graze on.

The WDT coordinated with government livestock officials on Koh Samui to have the owner of the riding school investigated for animal neglect.

In an update, the WDT said legal action was being prepared against the owner.

The WDT said: 'WDT thanks the Animal Welfare Division and Veterinary Services, Department of Livestock Development, for visiting Koh Samui to gather information and evidence and preparing to take legal action.

'The owners were renting out the horses for riding without caring for animal welfare and leaving them sick, skinny, and starving. They also used pregnant horses without regard for animal welfare.

'This case has caused heartbreak and sorrow from the concerned foreigners and everyone who learned about the loss of many horses previously from being used hard and not paying attention to maintenance.'

The nonprofit added that the Animal Health Development Group and the Koh Samui Livestock Office were checking the health of the remaining horses.

They said the relevant state agencies were coordinating with both Thai and foreign animal lovers to arrange for the food, care, and shelter of the rescued animals.

Tourism was the main source of income for many businesses on the idyllic island, regularly visited by celebrities including Katie Price, Beyonce, Kate Moss, and the late Shane Warne. Former footballer David Beckham reportedly even once owned a home there.

However, tourism has struggled to recover as quickly as other parts of the country due to the high cost of reaching the island. Many former businesses remain shuttered.