BANGKOK - Thailand's Crown Prince led tens of thousands of blue-clad cyclists through Bangkok on Sunday in a rare high-profile public appearance amid anxiety over the health of the ailing king.
Prince Maha Vajiralongkorn, 63, headed the first group of cyclists at the "Bike for Mom" event in the capital's historic quarter - a celebration of the role of his elderly mother Queen Sirikit.
Bangkok has been awash with blue T-shirts bearing the slogan "Bike for Mom" since her 83rd birthday last Wednesday - blue is the official colour of the Queen, who is hospitalised with her husband.
The tightly-choreographed event thrusts the crown prince centre stage at a time of heightened concern over the health of his revered father - 87-year-old King Bhumibol Adulyadej - as well as over the political and economic fortunes of the country.
The crown prince, in cycling lycra, helmet and sunglasses, was followed by a who's who of Thailand's key political players including Prime Minister Prayut Chan-O-Cha, and several other junta members.
The powerful head of the privy council, Prem Tinsulanonda, watched the start of proceedings from under an awning as crowds shouted "Long live the crown prince!" Palace doctors last week revealed the king has been treated for water on the brain and a chest infection at Bangkok's Siriraj Hospital.
Fears over the future - with elites competing for influence as Bhumibol's reign enters its twilight years - are seen as a factor behind a decade of political turmoil.
In recent years Prince Vajiralongkorn has spent much of his time away from the public eye.
But he has stepped in at some official ceremonies as his father's health declines.
"It'll be my first time to see the prince in my life... I'm happy", said cyclist Sirikarn Bamrungjit, 39, shortly before the race started.
The 43km event, which is taking place across the country, aims to break the world record of 72,919 people for a mass cycling event. The record is currently held by Taiwan.
But it is also billed as a chance to promote unity among Thais 15 months after a coup swept away the civilian government- the latest episode in a seemingly endless succession of elections and coups.
Before the event began, Prayut - who led last year's coup - saluted the crown prince and said the event was to "show our love for royalty".
Prayut justified the toppling of the elected government as necessary to end months of protests and to combat corruption.
The army also depicts itself as the defender of the monarchy, winning the support of arch-royalists who dominate Bangkok's elite and the southern portion of the country.
It has overseen a surge in the number of prosecutions under Thailand's draconian lese majeste laws.
A man was jailed for 30 years this month for "insulting" the monarchy on Facebook, in one of the toughest known sentences for royal defamation. The same day a woman received a 28-year jail term for the offence.