Thai king, longest-reigning monarch, marks 88th birthday

The world's longest-reigning monarch, Thailand's King Bhumibol Adulyadej, has turned 88 but celebrations were subdued due to his ill health.

Thais gather to pay homage for the ailing Thailand's King Bhumibol Adulyadej at Siriraj hospital where he lives on his 88th birthday Source: Getty Images

The people of Thailand have marked the 88th birthday of their king, the world's longest-reigning monarch.

Their beloved once-vigorous leader was in hospital and has not been seen in public for three months, so the celebrations were the most subdued in memory.

King Bhumibol Adulyadej looked frail on his last appearance before the general public on September 1, when he was taken on a brief tour of the Bangkok hospital where he has spent most of the last six years.

A Thai woman prays for the ailing Thailand's King Bhumibol Adulyadej Source: Getty Images

His most recent ailment was a lung infection that required him to be fed intravenously and use a machine to aid his breathing.

Many public activities were being held for the royal birthday on Saturday, but there were no joyous celebrations of the type that used to be held before the decline of the king's health.

While he is a constitutional monarch with no formal political role, the king has reigned for 69 years, making him the world's longest reigning monarch as well as the world's longest serving head of state.