Sections of Bangkok's normally choking streets turned into a sea of blue yesterday as Thailand's Crown Prince Maha Vajiralong-korn led tens of thousands of cyclists through the city in a tribute to his mother.
In a rare public appearance, the 63-year-old Prince donned a helmet and shirt in sky blue - the colour associated with Queen Sirikit - and rode through a 43km loop of streets specially closed for the occasion. The Queen, whose birthday is celebrated as Mother's Day in Thailand, turned 83 last Wednesday.
Security was tight as the Prince kicked off the mid-afternoon ride from inner Bangkok, accompanied by Prime Minister Prayut Chan-o-cha as well as several officials in the military government.
The heir apparent smiled and waved to hordes of well-wishers along the route.
Some participants bought bicycles specially for the occasion, while onlookers waited in the heat to catch sight of the Crown Prince.
Bangkok resident Ratree Srinuthum, 46, camped out on the sidewalk some three hours before the event.
"I'm excited," she said. "It's usually hard to get this close to him."
Similar mass rides were conducted nationwide on the same afternoon, in an event heavily promoted by the government weeks ahead.
Officially, the event has been pitched as a show of unity in the politically riven nation.
Newscasters were asked to appear on all TV channels in the sky blue polo shirt emblazoned with the "Bike for Mom" event logo, while Cabinet members dressed similarly for meetings.
Large portraits of the Crown Prince next to his mother were erected nationwide. A mass rehearsal was conducted two weeks before the ride.
The Prince himself was featured practising riding around a royal garden in a video that was released last Thursday.
The publicity blitz has thrust the heir apparent into the spotlight while concerns about the health of 87-year-old King Bhumibol Adulyadej refuse to fade.
The King, who is seen as a demigod and unifying figure in the country, has spent much time in Bangkok's Siriraj Hospital since 2009, when he was admitted for a lung infection.
Last Monday, the royal palace announced that he was recovering from excess fluid in his brain and lung inflammation.
Yesterday's procession of riders featured both serious hobbyists and beginners normally relegated to back roads in the capital's congested streets.
Chiang Mai University historian Attachak Sattayanurak observes that while King Bhumibol was closely associated with projects to improve agrarian society, yesterday's event allowed the heir apparent to reach out to the country's middle class, among whom biking is fast gaining popularity.
Analysts attribute Thailand's past decade of political turbulence to the conflict between the country's old elites and the "emerging middle class" based outside Bangkok.
Open discussion about the monarchy is rare in Thailand, where insulting or defaming the king, queen, heir or regent can land someone in jail for up to 15 years.
Since coming to power through a coup in May last year, the military government has tried lese majeste offenders in military courts, where there is no right of appeal. The number of convictions has spiked.
In the most recent case on Aug 7, a man was sentenced to 30 years' jail on six counts of lese majeste. On the same day, a woman was jailed for 28 years for the same crime.