The fire took place at 3am Sunday and caused minor damage to the front door of Dr Niran’s clinic in Muang district.
Forensic police inspected the scene and found traces of paper, a towel and a soft drink bottle used to carry petrol that was used in the attack.
Pol Lt Col Samart Srisunon, of Ubon Ratchathani’s forensic science office, said the attack appeared only to threaten Dr Niran as the arsonist scooped water from a nearby fish basin to put out the fire as it began to spread from the door into the clinic.
Rescue workers were alerted to the fire by Dr Niran’s neighbours and arrived at the clinic after the flames had been extinguished, Pol Lt Col Samart said.
Dr Niran, who is chairman of the NHRC subcommittee on civil and political rights, believed the arson was politically motivated as he was investigating violent gun and bomb attacks against the People's Democratic Reform Committee protesters. He blamed those who were discontent with the NHRC’s probe for the attack.
Dr Niran insisted that he was only performing his duty and not favouring any political group.