The 25-year-old sea turtle fell into a coma after a second operation on Sunday, following intestinal problems. Named Omsin, meaning "Piggy Bank", she was found to be eating coins thrown into a public pond where she lived, in Chonburi province.
The unusual mass of metal had cracked her shell.
By the time they were removed, she was carrying 5kg (11lb) of coins. The unusual mass of metal had cracked her shell, making the initial seven-hour operation necessary.
Omsin's demise prompted sadness everywhere
She was said to have been doing well after that surgery but developed blood poisoning at the weekend, which doctors said was the cause of death.
The coins were thrown into the pond by visitors hoping for good luck - a practice some hope will become less common after widespread coverage of the case in Thailand.
Omsin's demise prompted sadness and soul-searching. Many took issue with "merit making" practices common in Thailand, that sometimes harm animal welfare.
Hopes had been high for Omsin's recovery. Even after she slipped into a coma, the surgeon leading the team trying to save her said they wouldn't give up.
Doctors said the removal of the coins had created a space in Omsin's stomach that had probably blocked blood flow in her intestine. That became fatal after she suffered an acute intestinal infection.