Thailand’s revered ruler – whom many believe could have brought some calm to the political storm shaking his country – has had to cancel his annual state-of-the-nation address because of illness. It is the first time in more than 60 years that King Bhumibol, who turns 81 on Friday, has not delivered the traditional speech, which coincides with his birthday.The world’s longest-serving monarch has a history of heart trouble and underwent surgery two years ago. Many Thais were hoping he would issue a call for unity amid the political turmoil, days after former Prime Minister Somchai Wongsawat and his ruling party were ousted by the Constitutional Court. That followed an eight-day siege of Bangkok’s airports, including the busy international hub, Suvarnibhumi, by anti-government protestors. Normal airport activity finally resumed after demonstrators abandoned their sit-in. However, the opposition has warned it will strike again if parliament chooses a new premier too close to the former one. It is unclear when parliament will meet to select a successor after a session planned for next week was cancelled.