Unknown assailants opened fire on Mongkutwattana General Hospital on Chaeng Wattana road on Friday night, damaging a section of floor but causing no injuries.
Maj Gen Dr Rienthong Nanna, the hospital director, wrote on his Facebook that the attack took place at about 8pm when an unidentified gunman shot at the hospital, which is opposite a rally site.
He condemned the attack, saying hospitals have never been targets even during World Wars or in other battles.
"The hospital has treated not only anti-government protesters but also their opponents without any discrimination. The hospital has employees who both support and oppose the protests yet are able to work harmoniously together," he said.
He will not file a complaint with police about the attack because he does not have confidence and trust in the caretaker government and wishes to ask for protection from the army units deployed in Chang Wattana area.
The doctor also posted a photo of a hole he said was caused by the shooting.