Mr Harris, 53, has been at Vachira Phuket Hospital in Phuket City for 10 months after a motorcycle crash. He cannot talk and is not yet capable of fending for himself.
What has alarmed the hospital senior staff is the disappearance of a 640,000 baht disability payment that could have put Mr Harris on a flight home.
The hospital's international matron, Methavee Maneesri, is holding Mr Harris's passport because a second cheque for a 740,000 baht disability payment is now waiting to be claimed at a Phuket bank.
''If George loses this money, he will lose his chance to fly home,'' Khun Methavee said today. ''We are in a difficult situation and unsure about who we can trust.''
Earlier this year, Mr Harris's brother Hal and hospital staff shared hopes for George's transfer back to the US. but Khun Mathavee has opted not to give George's passport to Hal since discovering that George's signature had been forged on a document at a Patong bank.
''George has not been able to leave the hospital for 10 months so it was not George who signed for the money,'' she said.
At the time, Hal Harris had George's passport but returned it to the hospital when it was needed for documentation in preparation for a medivac flight home.
All planning for George's return has now ceased as Vachira Phuket awaits news from the Krungtep Bank about the disappearance of the first large disability payment.
Insurance payouts from the motorcycle crash covered George's brain surgery but he is still unable to talk and not capable of making decisions.
The hospital is prepared to waive the unpaid 400,000 baht in medical costs so far if George can be put safely on a medivac flight home and has someone reliable waiting at the other end in Dallas, Texas.
''We are not holding the passport as blackmail but for George's safety,'' Khun Methavee said today.
The hospital and George's brother Hal joined in a Phuket newspaper campaign to raise money to help fly him home in April.
Only later did the hospital discovered that the large cheque intended for George had disappeared in February, Khun Mathavee said.
''The US Embassy has been unable to provide answers about George's future care,'' Khun Methavee said. ''It's a very upsetting case. George appears to have been a victim twice.
''We aim to make sure that George does not become a victim for a third time.''
According to Khun Mathavee, the embassy suggested that George be reported to the Immigration Department as an overstay and that would start the process leading to his return to the US.
However, Khun Mathavee does not accept that as a solution because, with his brother Hal no longer considered trustworthy, George would still be without anyone to care for him.
''He could be here for years if there is no resolution,'' she said. ''But if that is what it takes, it may be the only way we can protect George.''