The plain-clothes police and soldiers were polite but firm as they led the middle-aged woman away. Her offence? Wearing a T-shirt with the slogan "Respect my vote".
One month after the Thai army seized power in a coup d'etat, citing potentially severe conflict after more than six months of deepening political gridlock, it has the country sewn up tight.
The flash mob protests and heavy troop deployments seen in the first fortnight after the coup have vanished. Protests since then have been occasional and low-key - and arrests swift. With the nationwide curfew imposed on May 22 lifted this month, life has returned to normal and tourism is showing signs of recovering after a sharp fall.
More than 500 people including academics and journalists have been summoned to report to the army's National Council for Peace and Order. It is not known how many have been detained and released.
The Constitution remains suspended and martial law allows detention without charge for up to seven days.
The army stressed that detention conditions are comfortable though the detainees are isolated. "We want to adjust their thinking," an army spokesman, Colonel Werachon Sukondhapatipak, has said.
There have so far been no systematic violations of human rights such as torture or extrajudicial killings, according to Mr Sam Zarifi, Bangkok- based Asia-Pacific regional director of the International Commission of Jurists.
"The military is trying very hard to stay within the bounds of martial law itself," he said.
However, he added: "Restrictions on freedom of expression have included warnings to journalists and the media, and threats to prosecute people for peaceful speech. This is the most serious concern."
The military junta has extended control on a wide front, from Bangkok's notorious traffic to the boardrooms of big state corporations. It is weeding out people in key positions it considers dissenters.
It has pledged a social order campaign which includes cracking down on illegal loggers and other criminal mafia. And it has held street parties and given out free tickets to a just-released patriotic historical epic film, in a drive to "bring back happiness". It has also assured the international investor community that Thailand remains in business.
Pending investment projects stalled by six months of political gridlock are being cleared.