The banner measuring 6 by 20 metres was installed around 4pm Friday by the Student Federation of Thailand, Network of Social Activists for Democracy, Free Thammasat Group for Democracy and Wan Mai Group.
The wrapping bore the message "20 million + 3", a reference to the people who cast votes on Feb 2 and the three judges who voted against voiding the results of the poll.
The charter court judges ruled 6:3 that the vote violated the constitution because voting was not all held on the same day.
The activists said the court lacked the authority to decide by a 6:3 vote on the issue, and the ruling showed no respect to the 20 million citizens who turned out to cast their votes on Feb 2.
However, some people disagreed with the protesters and tried to remove the banner. Later the student-led group left without a confrontation.