The protests against the monarchy, the government and Prime Minister Prayuth Chan-Ocha, who took power in the country after a coup in 2014, lasted throughout Saturday.
- Down with feudalism, long live the people!
shouted the crowds.
Saturday's protest, which takes place on the anniversary of the coup, is said to draw inspiration from, among other things, Hong Kong's democracy protests.
It has been dominated by students but so far lacks a clear leader.
"One of the turning points"
The thousands of protesters marched during the day from the university towards Sanam Luang Square outside the Royal Palace.
Among other things, the majority of rainbow flags were seen in the crowd, which is still a controversial symbol in parts of the country.
"This day is one of the turning points in Thailand's history," said 29-year-old Patipat, one of the protesters gathered at the square.
On Saturday afternoon, protesters had set up tents where curious people could buy everything from t-shirts to flags to express their support for the protests.
At the same time, thousands of police gathered on the outskirts of the square.
Several of the protesters have stated that they intend to spend the night in the square and then walk towards the government building on Sunday morning.
Local authorities have warned that the protests will meet with police resistance if this happens.
Requires new election
Demonstrations in the country have been going on since July and the protesters are judging the elections held last year.
The election led to the coup leader from 2014, Prayuth Chan-O-Cha, remaining as prime minister.
During the summer months, government-critical demonstrations were organized by student-led groups almost daily.
They demand more democracy, a rewritten constitution, the resignation of Chan-O-Cha and new elections.
Recently, the demonstrations also raised demands for the abolition of the law protecting King Maha Vajiralongkorn and the country's monarchy.
Criticism of the royal family has long been taboo even among opposition figures.
The Prime Minister has called the demands "unacceptable" for a majority of Thais.