Thailand's 88-year-old King Bhumibol Adulyadej, the world's longest reigning monarch, is in an unstable condition after receiving haemodialysis treatment, the palace said in a statement late on Sunday, Reuters reported. News about the king's health is closely monitored in Thailand, where King Bhumibol is deeply revered. The king has been treated for various ailments over the past year at Bangkok's Siriraj Hospital - his home for much of the past year - and was last seen in public on Jan. 11, when he spent several hours visiting his palace in the Thai capital. Anxiety over the king's health and an eventual succession has formed the backdrop to more than a decade of bitter political divide in Thailand that has included two military coups and often-violent street demonstrations. Sunday's statement was the second health bulletin this month after the palace said on Oct. 1 that the king was recovering after a respiratory infection.