His Majesty the King has been advised to put off royal activities for a while after developing a low fever and feeling tired, the Royal Household Bureau says.
In its 59th statement, the bureau said His Majesty has suffered a low fever from time to time during the past week.
His appetite has diminished and he has experienced fatigue.
A team of royal physicians at Siriraj Hospital has provided medical check-ups on a daily basis since His Majesty developed the fever.
His heartbeat and blood pressure are normal, but his breathing is slightly faster than normal.
Yesterday, His Majesty felt pain in his knees and an examination showed both knees were swollen. A blood test indicated no bacterial infection so doctors provided him medication to treat the swelling.
His Majesty is scheduled to preside over the opening ceremony of the King Chulalongkorn statue and the opening of the Sayamindradhiraj Medical Institute on Friday.
Siriraj Hospital will host a monkey show for His Majesty at the end of the ceremony.