Student activist Rangsiman Rome was arrested in Bangkok on Sunday and sent to hear charges of campaigning against the charter referendum in Samut Prakan province.
Chana Songkhram police detained the New Democracy Movement member on Tao Nao Road near the Oct 14 Memorial, where he was to attend a fund-raising event organised by the group to help political prisoners.
The Thammasat University student was taken to the police station and later sent to Bang Sao Thong police station in Samut Prakan's Bang Sao Thong district, the group said on its Facebook account.
Bang Sao Thong police issued an arrest warrant for him and 12 other activists for launching a campaign for voters in the area to throw out the draft charter in the referendum held on Aug 7, 2016. The draft charter sailed through the vote.
His arrest took place one day before the group will submit a petition at Government House demanding the government disclose details of the Thai-Chinese train project.