An post-mortem revealed 80 plastic luggage weighing as much as eight kilograms (18 kilos) within the creature's abdomen, the division added.
Thon Thamrongnawasawat, a marine biologist and lecturer at Kasetsart University in Bangkok, told Agence France-Presse that the plastic probably prevented the whale from digesting food.
Volunteers and veterinarians worked for several days to save the wale.
Thailand is one of the world's biggest users of plastic bags, according to The Guardian. While the plight of the whale garnered huge sympathy as well as anger from the Twitterati of Thailand, it remains one of the world's top-five plastic polluters, according to a report by the nonprofit environmental advocacy group Ocean Conservancy.
The small male pilot whale had been discovered ailing and unable to swim in the Na Thap Canal last Monday.
Dr. Thon said he was urging the Thai government to do the same.
Experts believe the pilot whale, which would normally feed predominantly on squid, thought the floating plastic bags were food.
"We don't want to be the country that everyone blames in the future if we do nothing", he said.
Countries including the United Kingdom and India are banning straws and single-use bags, and forcing supermarkets to impose levies on plastic bags. Plastic has been taking lives of a lot of habitat, marine life to be specific. Kenya a year ago enacted the world's toughest law against plastic bags.
He said that at least 300 marine animals die in Thai waters each year after eating plastic.
"We are facing a serious crisis", he said.