Observers expect the anti-government protests to continue but without escalating into violence.
Jatuporn Prompan, chairman of UDD, said on Sunday there was still a long way to go for the student-led movement, especially their demand for the constitution to be rewritten.
Speaking on his show on Peace TV, he said that curbing the powers of the military-installed Senate and revising the election system would not come easily.
Mr Jatuporn also warned that the use of legal tools against the demonstrators will not solve the problem and only attract more people to the movement.
He said the red-shirts turned up at the Saturday rally in droves because they oppose dictatorship and have lived in agony over the past several years following the military crackdown. However, he did not join the rally because his presence would have prompted security authorities to intensify their response plan.
Academic Somjai Phagaphasvivat said the students are initially deliberately maintaining a less aggressive stance in order to gradually build momentum and put pressure on the government.
"They have paused to see how the government responds. The economy is unlikely to be affected [by the rally]. The economy is affected by the Covid-19 pandemic," he said.
After the overnight rally at the site, the protesters on Sunday morning staged a ceremony to install a new plaque at Sanam Luang, which literally means "the royal ground", to declare it as the property of the people.
The protest ended after Panusaya Sithijirawattanakul, the co-leader of the United Front of Thammasat and Demonstration, presented a list of their demands for reform of the monarchy to the Privy Council president via Metropolitan Police Bureau chief Pol Lt Gen Phukphong Phongpetra.
The activists plan to gather again on Thursday outside parliament, while another student leader, Parit "Penguin" Chiwarak, has called on the public to take part in a general strike on Oct 14 -- the anniversary of the 1973 student uprising.
Prime Minister Prayut Chan-o-cha thanked both security officials and the protesters for their cooperation in maintaining law and order during the rally, government spokesman Anucha Burapachaisri said.
The rally attracted between 30,000 and 50,000 people at its peak on Saturday night but there were no serious incidents.
Some officials, however, have pointed out to the protesters' violation of certain laws. Among them, Fine Arts Department director-general Prateep Pengtako told Matichon newspaper the department would file a complaint with police against the protest leaders for violating Act on Ancient Monuments, Antiques, Objects of Art and National Museums, which protects Sanam Luang.
Tida Tawornseth, an adviser to the red-shirt United Front of Democracy against Dictatorship (UDD), said the two-day protest over the weekend demonstrated the responsibility and consideration of the leaders and supporters.
"I believe they well understand [their mission]. They are just holding short protests without any rush for change and leaving society to contemplate [the issues]," she said.
To create a win-win situation, government officials should consider the proposals rather than take legal action against the protesters which might result in violent retaliation, she said.
However, Sirichai Maingam, former leader of the yellow-shirt movement, said the student-led protest had failed to gain wider support partly due to their demand for reforms of the monarchy.
"It appears the student leaders don't know what they want. They demand the prime minister's resignation and House dissolution without saying more. They call a new rally on Sept 24 but what do they have to retain the supporters?" he said.
Mr Sirichai said the red-shirt turnout at the rally could also make potential allies turn away with doubts whether the movement is ideologically driven or politically motivated.
He said political parties will not openly support the movement because they do not think it will succeed.
"Laying the plague is just an activity. As long as the public isn't convinced, it's just a play on words. People will still call it Sanam Luang. Social mobilisation depends on experience and crystallisation of ideas," he said.
