For much of his remarkable seven decade reign, Bhumibol's 5 December birthday was an auspicious moment for Thais with the monarch often delivering key speeches offering social -- and sometimes distinctly political -- guidance in a nation buffeted by years of coups and instability.
Stricken with ill health in the last decade of his life, he missed his last two birthday appearances before his death aged 88 on October 13.
"I still feel lonely and empty as we don't have him anymore," a visibly moved Yaowana Kaewpud, one of the mourners on the bridge, told AFP.
The 47-year-old and her daughters had travelled from the outskirts of Bangkok to attend today's dawn ceremony, which featured black-clad mourners giving alms to 999 monks.
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Bhumibol was widely revered as a calming constant and afforded a near god-like status among many Thais through his many years criss-crossing the nation, a reputation further burnished via a slick palace propaganda machine.
His passing is a delicate transition both for the monarchy and its backers in the military elite.
Bhumibol forged a strong alliance with Thailand's coup-prone generals, who often used perceived threats against the monarchy to seize power in putsches that were almost always recognised by the king.
His reign saw breakneck development but also entrenched disparity between a Bangkok-centric elite and the rural poor.
In the last ten years Thailand has been torn apart by competing political factions representing those two sides.
The 64-year-old prince ascended the throne last Thursday after a seven week hiatus in which he asked to be allowed time to mourn his father.
He is comparatively unknown to ordinary Thais, choosing to spend much of his time outside the kingdom and has not given an interview for years.