This is the heartwarming moment a hero passerby hopped in a boat to save a drowning pet dog.

The pooch had fallen into the choppy river next to a restaurant in Nonthaburi province, Thailand, on Tuesday (February 15).

Diners continued eating their food, unaware that the mixed-breed Golden Retriever was struggling to stay afloat just a few yards away.

However, a quick-thinking food trader jumped into his wooden long-tail boat with his wife and they gently floated over to the animal.

Footage shows how the dog clung desperately to the boat with its paws while catching its breath. The man then guided the vessel to a nearby ledge where his wife climbed out and began treating the dog, which was exhausted from paddling in the Chao Phraya River.

A resident emerged from the nearby homes and began rubbing the pooch to help it recover. They later took the dog home with them to care for it.

Onlooker Thitsana Chitsaiyen said: 'I was eating lunch when I noticed the dog in the water. I also called out to one of the food sellers that had a boat and they went to help it.

'The dog was so tired from being in the river. I felt so sorry for him. I'm relieved we were able to save him.'