More than 13,000 people gathered at Suan Rot Fai park in Bangkok in their running gear even before sunrise yesterday.
But they were not gearing up for a marathon.
On their running bibs, there were stickers with cheeky remarks such as "Sick of the uncle", "We don't hate the country; we just hate you", and "What's harder to get rid of than my belly is the uncle".
They were taking part in a 4km run to "chase out the uncle", referring to Thai Prime Minister Prayut Chan-o-cha, who is commonly known as "Uncle Tu".
Titled "Run Against Dictatorship" in English, this was Thailand's first anti-government protest in the form of a running event.
It was organised by dozens of university students to express dissatisfaction with General Prayut, who staged a coup in May 2014 before winning his second term as prime minister in the March general election last year.
His continued leadership was thanks to the success of the pro-military Palang Pracharath Party that nominated him and the rubber-stamp Senate that voted him in.
"We only want to voice our frustration. It's not meant to be a prolonged protest aiming at toppling the government," economics student Thanawat Wongchai, 21, of Chulalongkorn University who led the group, told The Straits Times.
"He (Prayut) should know what to do after seeing the massive support for the event."
Another participant, Mr Thanawut Putsri, woke up at 3am to join the run from the neighbouring province of Samut Prakarn.
He closed his shoe shop on his busiest business day, saying he felt he had to come because "politics has clearly gotten too divisive".
Office worker Nariya Pimolwattana, 31, said: "Since the coup, I feel that things have been really unfair.
"The pro-military side can do whatever they want without consequences, but the pro-democracy side has been blocked in everything we do."
She is a supporter of the Future Forward party, which is known for its anti-military and progressive stance, and is facing possible dissolution on Jan 21. The Constitutional Court is set to rule then on whether to dissolve the party, the third best performer in the March election with 75 seats in Parliament
This followed an allegation that the party is seeking to overthrow the constitutional monarchy and that it has ties with secret society Illuminati.
The court is also deliberating another case against the party over its leader Thanathorn Juangroongruangkit's series of loans worth 191 million baht (S$8.6 million) to his party last year.
Mr Thanathorn, who joined yesterday's run, told reporters: "To be able to be a democratic country again, the first step is that General Prayut has to get out.
"The people here today share this feeling. This is the demonstration of the anger of the people."
Before the run, organisers had to relocate their press conference twice and the run itself after being pressured out of the venues.
Those planning to join similar runs outside Bangkok also reported being intimidated by police.
Dr Wanwichit Boonprong, a political science professor at Rangsit University, said: "The authorities may feel that if they allow more people to join, the network would get bigger and it would be harder for them to control the situation.
"This is a new way to protest without risking confrontations and violence. It's a short event not involving too many people."
There was also a counter protest which saw thousands joining a walk in support of Gen Prayut at Bangkok's Lumpini Park, around 14km from Suan Rot Fai.
As drums played, the crowd chanted "Uncle Tu Fight Fight".
Among those who took part was Ms Jirada Hongkhananukroh, a housewife. She said of the Thai PM: "I'm confident that the uncle will continue to lead the country well."
"I don't like dictatorship either and I also support democracy. But it is not dictatorship as many people claim. Winning the popular vote means it's certainly not dictatorship," she added, referring to the 7.9 million votes Palang Pracharath received last March, the biggest number for a single party.