Dozens of tourists were rescued after being left adrift at sea when their boat's anchor rope snapped.

Eighty-five life vest-wearing holidaymakers floated in the waters near the Emerald Cave in Trang province for 30 minutes when the vessel they had boarded began drifting away on May 6.

Footage shows the tourists forming a snaking queue near the cave's entrance, holding onto each other as they awaited rescue.

Another boat later arrived to pick them up, but the people onboard had to descend first to prevent overcrowding.

There were no casualties reported, but the incident has raised concerns over safety regulations for tourists in the notoriously undeveloped Southeast Asian country.

Tourist Watakan Somchai said: 'Everything was alright when we entered the cave, but when we came out, the rope was torn, causing the boat to float far away. We tied it to a rock because we didn't want to drop an anchor and damage the corals.

'While we were waiting for rescue, another boat came by, but its passengers had to go down first.

'It was raining on the other side of Koh Kradan island so the waves were strong, but the tour guide and the boat team took very good care of us.'