The people of Thailand yesterday marked the 88th birthday of their king, the world's longest-reigning monarch, but with their once-vigorous leader in a hospital and unseen in public for three months, 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 Bangkok's Siriraj Hospital, where he has spent most of the last six years. 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, but there were no joyous celebrations of the type that used to be held before the decline of the king's health. One major gathering point this year was outside the hospital that has become his de facto palace, where well-wishers came to offer their prayers. The king's other medical issues in recent years have included excess fluid in the brain and an operation to remove his gallbladder. A sombre reminder of his generation's passing came yesterday morning with the death of 96-year-old former foreign minister Siddhi Savetsila. While he is a constitutional monarch with no formal political role, Bhumibol - King Rama IX - has generally been regarded as Thailand's unifying figure. His intervention during major political crises is generally seen as having been key to restoring the status quo. Before the decline in his health, Bhumibol's birthday had also been the occasion for a much-anticipated annual speech in which he would speak his mind to exercise his authority as the country's moral leader.