Crowds have begun to swell outside the Siriraj Hospital in the Thai capital, Bangkok, to hold a vigil for King Bhumibol Adulyadej amid mounting health concerns. The 88-year-old, who is the world's longest reigning monarch, has been undergoing medical treatment for various ailments, but his condition has deteriorated.

Scores of people, wearing yellow and pink – considered to be auspicious colours – were seen sitting on the ground and reciting prayers in the early hours of Thursday (13 October). The Thai palace said the royal's overall health condition is still unstable.

In its 38th statement released on Wednesday (12 October) night, Thailand's Royal Household Bureau said the king is still suffering from blood infection and abnormal liver function. It added that he remains on ventilator and is receiving continuous renal replacement therapy (CRRT), which is given only to critically ill patients.

During the day-long events on Wednesday, Thai Prime Minister Prayut Chan-ocha cut his visit to another part of the country short and returned to Bangkok, prompting a flurry of rumours. The king's children –including Crown Prince Maha Vajiralongkorn who also cancelled his scheduled events – were also at the hospital, leading to further speculation.

However, the junta government's spokesperson said the Thai premier returned to Bangkok to hold a "routine presentation" with the heir-apparent on government matters.

Thai social media has turned yellow and pink with messages pouring in for the king, who is revered as a fatherly figure in a politically turbulent country. He has been at the hospital for the most part of 2016 and was has not been seen in public since January.

The royal, who came to the throne in 1946, has been at the helm for seven decades during which time the country witnessed bloody military coups and political turmoil. The Thai public often see him as a symbol of unity and stability in testing times.