About 100 people demonstrated in front of Major Ratchayothin shopping mall against the coup.
They gathered at 11 am and many held a banner, saying "Take the coup back to barracks, and return the people's power".
The demonstrators also booed at troops deployed to keep security.
While they were protesting against coup, a woman walked through them to express moral support to the troops, leading to a brief confrontation. The woman was later escorted away by police.
The demonstrators later dispersed after the commander of the troops there announced that they would be arrested for violating the martial law if they did not stop.
The demonstrators vowed to return to hold more rallies in front of the shopping mall.