At least 24 persons were injured in an explosion in Phramongkutklao Hospital in Bangkok on Monday, police said.
The blast took place in a reception room, Xinhua news agency quoted Saroch Kheawkhajee, chairman of the Army Medical Department, as saying.
A gas leak or an air compressor may have caused the explosion, he said.
An investigation has been initiated to determine the exact cause of the incident.