"Luang Pu is feeling very weak and generally sick after the Centre for the Administration of Peace and Order (Capo) fired tear gas canisters at him yesterday," the message says.
Doctors prescribed bronchodilators, medication to reduce swelling in respiratory passages and antihistamine for the monk.
Reports said Luang Pu, who is the protest leader at the Chaeng Wattana site, will lodge a complaint with Thung Song police against Capo this morning.
On Friday afternoon, police fired tear gas and water cannons at Luang Pu and anti-government protesters outside the Police Club which is being used as offices by Capo.
The protesters dismantled a barbed wire barricade set up in front of the club grounds.
The monk announced he would give Capo five minutes to send out a representative to talk to him.
After the time lapsed, he walked into the Police Club grounds.
The police warned them through speakers to stop trespassing, saying the protest was illegal.
They then used water cannon and fired tear gas canisters at the protesters, who backed away.
The monk was injured and escorted away from the area by guards for first-aid treatment.
Bangkok Metropolitan Administration's Erawan medical centre reported two men and two women were injured and sent to Vibhavadi Hospital for treatment.