Bhumibol is the world's longest-reigning monarch and beloved by many in Thailand.
The palace tightly controls news about his health and it is difficult to ascertain his overall condition.
The latest statement issued by the Royal Household Bureau on Saturday night said he was recovering from a respiratory infection in his left lung after being treated with antibiotics.
"Today he has no fever and his breathing is normal
Bhumibol has been treated for a variety of health complications over the past two years, including bacterial infections, breathing difficulties, heart problems and hydrocephalus -- a build-up of
His reign has spanned seven tumultuous decades and his frail health is a cause of great public concern for Thais, most of whom have never known life under another king.
He is also shielded by one of the world's harshest royal defamation laws, which has been used to jail scores of Thais for
Analysts say anxiety over the end of Bhumibol's reign has aggravated the past decade of political conflict in Thailand, with elites jostling for influence.
But open discussion of his legacy and the future of the institution is all but impossible because of the lese majeste law.