The green turtle named Omsin, "piggy bank" in Thai, underwent a seven-hour-long operation this month to remove 5 kg (11 lb) of coins which she had mistaken for food.
But Omsin, who lived at a conservation centre in Chonburi, east of the Thai capital Bangkok, was rushed into intensive care on Sunday night, breathing too slowly. She received an emergency operation on Monday, after which she went into a coma.
"Her cause of death is blood poisoning," one of the vets told reporters.
The gap in Omsin's stomach left by the removal of the coins caused her intestine to become strangled, blocking blood flow, the vets said. Acute infection in the intestine then caused blood infection.
They also said they would perform an autopsy on Omsin as a case study, which would benefit the treatment of turtles in the future.
"She is our teacher," another vet said.
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