Officials are working to resolve a computer system malfunction at Saraburi Hospital resulting from a ransomware attack.
The Royal Thai Police office said the attacker demanded a ransom of 63 billion baht in Bitcoin.
Saraburi Hospital director Dr Anan Kamolnate said it was true that the hospital's computer system was attacked with ransomware, but his assistant, Dr Thamrongsak Kongmun said no ransom figure had been given despite the hospital having been contacted by a suspected hacker.
On the hospital official's Facebook page, a message was posted saying the hospital computer system was experiencing a glitch which caused other connected networks to collapse.
The hospital said it was urgently trying to resolve the issue and asked patients to bring essential documents with them when visiting the hospital until the computer system was fixed.
Public Health Minister Anutin Charnvirakul said the ministry had called on the Ministry of Digital Economy and Society to install measures to counter cyber-attacks at hospitals nationwide.
The minister said the public should not be worried because hospitals are able to deliver vital medical services in the event of computer malfunctions.
He said hospitals have backup data.
The ministry has alerted other hospitals to the ransomware and instructed them to update their own computer software and programming protection, Mr Anutin said.
No other hospitals came under attack, he said.
The Royal Thai Police's deputy spokesman Kissana Phathanacharoen said Saraburi Hospital had filed a complaint with Muang police station.
The ransomware was detected after it entered the hospital's computer system on Sept 5 at 5.31am.
The computer virus made the hospital's patient database inaccessible, damaged all scanned patient medical records and rendered the hospital's landline telephone unusable.
Pol Col Kissana also said the attacker had made a 200,000-Bitcoin ransom demand.
Investigators and officers from the Office of Police Forensic Science have been to the hospital to inspect its computer system.
The Technology Crime Suppression Division is taking part in the investigation.