Around 200,000 people, lined the streets from Siriraj hospital, where the King has been staying for more than three years, to the Royal Plaza to join the birthday celebration.
Many of the yellow-clad and flag-waving well-wishers camped out in front of the hall since Tuesday evening, hoping to catch a glimpse of the King. Some of them shed tears as they kept chanting "long live the king."
In Thai culture, yellow is the color representing Monday, the day of the King's birth.
Queen Sirikit did not accompany the king for the grand audience at the hall on the advice of her doctors, according to a statement issued earlier by the Royal Household Bureau.
Last year, the monarch appeared on the main balcony at the Chakri Maha Prasat Throne Hall at the Grand Palace to mark his 84th birthday, calling for national unity and stability as the country just went through one of the greatest flood disaster in its history.
King Bhumibol came to the throne in 1946 and is now the longest reigning monarch in the world, widely revered across the kingdom. He was admitted to hospital in September 2009 for pneumonia and has since stayed there and rarely made public appearance.
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