The director of Saraburi Hospital on Wednesday confirmed the hospital computer system had been attacked with ransomware, but said no demand for money was received.
Patients were being advised to bring their own medical records and old medicine packaging with them if they visit the hospital.
Dr Anant Kamolnet, director of Saraburi Hospital in Muang district of Saraburi province, said computer system crashed due to a ransomware attack.
He denied reports the hospital management received a demand for 200,000 bitcoins (about 63 billion baht) to have its database restored.
No one had contacted the hospital to make a ransom demand, he said.
The hospital management announced on its Facebook page on Monday that a computer crash had stalled systems at the hospital. Staff were trying their best to solve the problem.
It asked patients to bring their welfare cards, copies of referrals, ID cards, medicinal allergy cards, old prescriptions and drugs for reference if visiting the hospital.