This is the dramatic moment a large waterspout was seen swirling along the ocean off the coast of a Thai island.

The tornado caused by an ongoing heatwave was seen by locals and tourists near Koh Si Chang in Chonburi, eastern Thailand this morning (April 30).

The huge waterspout, which was travelling at around 40mph, appeared two kilometres away from the island's most popular shore, Tha Wang beach at 6.30 a.m.

Village chief Arkom Tanyongmas, who captured the natural phenomenon, said that it was the biggest tornado that had ever happened on the island.

He said: ''There has been this kind of tornado before but I have never seen it so huge and scary like this.

''It may be caused by the unpredictable weather. It's very hot these days and it hasn't rained on the island for a week.''

The tornado lasted for 30 minutes before it finally dispersed. Nobody was reportedly injured and no damages were caused.

''Luckily, the storm didn't last long enough to hit the island. I couldn't imagine what would happen if it did,'' Arkom added.