A fire broke out at Khlong Prem central prison in Bangkok late last night, destroying three of the six buildings in the complex.
Reports from the emergency service say that the fire started at about 22.40pm in the fourth zone of the prison, which is used as the occupational centre for the inmates.
Several fire trucks attended the scene.
The prison also houses the Bangkok remand prison, which is used to hold political detainees, among them those charged with lèse majesté.
The fire was still burning at about 11.30pm, after three wooden buildings had been razed. There are currently no reports of casualties among the inmates.