Openly challenging the monarchy of Thai King Maha Vajiralongkorn, thousands of protesters marched in Bangkok on Sunday to present demands that include a call for reforms to curb his powers.
Protesters have grown ever bolder during two months of demonstrations against Thailand's palace and military-dominated establishment, breaking a long-standing taboo on criticising the monarchy - which is illegal under lese majeste laws.
The Royal Palace was not immediately available for comment. The king is not currently in Thailand.
The marchers were blocked by hundreds of unarmed police manning crowd control barriers.
Protest leaders declared victory after saying Royal Guard police had agreed to pass on their demands to police headquarters. Police made no immediate comment.
"Our greatest victory in the two days is to show that ordinary people like us can send a letter to royals," Parit "Penguin" Chiwarak, told the crowd.
At the biggest demonstration in years, tens of thousands of protesters on Saturday cheered calls for reform of the monarchy as well as for the removal of Prime Minister Prayuth Chan-ocha, a former junta leader, and a new constitution and elections.
Shortly after sunrise on Sunday, protesters cemented a plaque near the Grand Palace in Bangkok in the area known as Sanam Luang, or Royal Field.
It reads, "At this place the people have expressed their will: that this country belongs to the people and is not the property of the monarch as they have deceived us."
Police did not intervene. Government spokesman Anucha Burapachaisri said police would not use violence against protesters and it was up to the police to determine and prosecute any illegal speech.
"Down with feudalism, long live the people," protesters chanted.
The plaque resembles one removed without explanation from outside one of the royal palaces in 2017, after Vajiralongkorn took the throne. That plaque, which had commemorated the end of absolute monarchy in 1932, was replaced by one with a pro-monarchist slogan.