Support is growing for the 14 students jailed by Thailand's military regime since June 25, and charged with sedition.
The Resistant Citizens Group, which has staged occasional small protests against the military regime, yesterday tried to hold a protest for democratic rights at the Bangkok Art and Cultural Centre.
This prompted the government to mount a massive security cordon around the building.
But the group defied the police. They jammed the walkway outside the cordon opposite the popular MBK mall to hand out free sandwiches and Post It stickers on which supporters wrote messages that they pasted on a partition board. The police looked on but did not make any arrests.
Most of the messages called for the 14 students to be freed.
The number of protesters - mostly middle-class Thais - seemed modest at first but after an hour, there were hundreds of stickers on the partition, and some were occasionally blown away by gusts of wind. The walkway, half of which was cordoned off by the police, was jammed with protesters, shoppers and tourists.
Charges of sedition against the students drew statements of concern from the United Nations and the European Union. The charge carries a seven-year jail term.
In a twist, the students have refused to apply for bail, saying they do not recognise the legitimacy of the army. This has deprived the army of a face-saving way out, analysts say.
Thailand's Prime Minister Prayut Chan-o-cha earlier this week was quoted as saying that he was "uncomfortable" with the situation and appeared to favour dialogue with the students but said the government could not show leniency.
Earlier yesterday, in a statement read outside Klongprem Central Prison where the students are being held, the Institute of Human Rights and Peace Studies of Mahidol University demanded that security forces stop intimidating, following or threatening family and friends of the students. They should be tried in a civil court, the institute said.
The students were arrested the day after they formed a new umbrella group, called the New Democracy Movement, comprising several small activist groups.
The 14 incarcerated students, whose average age is 23, will face a military tribunal on July 7.