Her Majesty Queen Sirikit was admitted to Chulalongkorn hospital after she developed a fever and cough, and has been diagnosed with influenza, the Royal Household Bureau announced.
In a statement dated Aug 19, the bureau said the Queen was found to be feverish, with frequent coughing, on Sunday morning.
Tests diagnosed influenza and she was administered medication, the statement said.
Since receiving treatment the Queen's general condition has improved. The fever has subsided, she is coughing less frequently and has a good appetite.
Doctors have asked her to stay at the hospital until she recovers fully, the bureau said.