The health of Thailand's 88-year-old King Bhumibol Adulyadej, the world's longest reigning monarch, has "overall not yet stabilized", the palace said on Wednesday.
The statement from the palace follows one on Sunday saying the king was in an unstable condition after receiving haemodialysis treatment, which is used to cleanse the blood of toxins, extra salts and fluids.
A Reuters reporter at Bangkok's Siriraj Hospital said all four of the king's children, including Crown Prince Maha Vajiralongkorn, visited him on Wednesday.
"On Oct. 11 his blood pressure lowered and breath quickened," the palace said. The king's health has "overall not yet stabilized," it said.
Several hundred people gathered at the hospital, where the revered king has been for much of the past year, to pray for him.
The government had earlier urged people not to listen to rumors on social media about "situations," saying they should await official announcements.
During his seven decades on the throne, the king, who is seen as a unifying force, has intervened when events threatened to plunge Thailand into crisis.
He has been treated for various ailments over the past year and was last seen in public on Jan. 11, when he spent several hours visiting his palace in the capital, Bangkok.