The group was allowed to enter the Parliament building in Bangkok's Dusit district, while policemen were deployed to ensure safety there.
The group is opposed to any amendment or abolition of Article 112 aimed at protecting the monarchy, saying that it was now an important factor whether people would support politicians or political parties.
The group urged senators not to be pressured into voting for the prime minister or political parties who plan to amend the law.
The group submitted its petition and the list of supporters to Senator General Akanit Muensawat before dispersing.