A post mortem found 80 pieces of plastic in inside it, weighing eight kilograms.
A whale has died after swallowing 80 plastic bags in southern Thailand.
The whale's death comes as dozens of cities and companies worldwide are moving to crack down on plastic pollution by banning the use of non-reusable plastic containers, bags and drinking straws.
Thai marine authorities attempted to keep the animal afloat and nursed it for several days before it died.
Photos posted by the group reveal tens of plastic bags that remained undigested throughout the whale's body.
Thai Prime Minister Prayuth Chan-ocha has declared improved waste management a national priority, and government agencies are evaluating ways to reduce consumption, an official said.
Marine biologist Thon Thamrongnawasawat told Agence France-Presse the bags would have made it impossible for the whale to eat nutritional food.
Thailand is one of the world's largest consumers of plastic bags for which hundreds of marine creatures living near the country's popular beaches die every year.
A team of vets tried to "help stabilise" the small male pilot whale after it was discovered on Monday barely alive in a canal near the Malaysian border, the department said. Thon said at least 300 marine animals including pilot whales, sea turtles and dolphins, perished each year in Thai waters after ingesting plastic. "We need to take action now".