The male pilot whale was found barely alive on May 28 in a canal in the province of Songkhla, near the border with Malaysia, and received treatment from a team of veterinarians.
Photos posted on the Facebook page for ThaiWhales, a local conservation group, showed volunteers trying to help the sick whale, shading it with an umbrella and attempting to give it medicine and fluids.
Volunteers and veterinarians worked for several days trying to save the mammal. But on June 1, the whale vomited five plastic bags and later died, the Marine and Coastal Resources Department said on its website.
An autopsy found 80 bags and other plastic items, weighing around 17 lbs lodged in the whale’s stomach, which made it impossible for the mammal to eat food, marine experts said.
Jatuporn Buruspat, head of the department, said the whale probably thought the floating plastic bags were food.
Pilot whales mainly feed on squid, but are known to eat octopus and small fish when squid are not available, according to the American Cetacean Society, a whale conservation group.
Jatuporn said his department planned to raise public awareness of the problem on World Oceans Day on June 8.
“We will use the whale case and invite all sectors to show their intentions on how to reduce the use of plastic in Thailand,” he told Reuters.
Globally, eight million tonnes of plastic – bottles, packaging and other waste – are dumped into the ocean every year, killing marine life and entering the human food chain, the United Nations Environment Programme said in December.
WATCH: Oceans may have more plastic than fish by 2050
— With files from Reuters