Thais will decide on Sunday whether to accept a new military-drafted constitution in the first vote since the generals toppled the elected government in 2014.
The military says its charter — the country’s twentieth — will curb political corruption and bring much-needed stability after a decade of turmoil.
But critics say the document is a shameless attempt to extend the army’s grip on power.
The grassroots Red Shirt movement is loyal to the ousted government of Yingluck Shinawatra and her brother Thaksin and is fiercely critical of the junta.
Today 19 Red Shirt leaders were charged at a Bangkok police station with breaching a ban on political gatherings of more than five people.
“They are all charged on one charge of violating the order,” Winyat Chatmoontree, a lawyer for the movement, told AFP.
The charges follow an attempt to open a referendum monitoring centre which was swiftly closed down by authorities.
The group were released pending trial, he said, adding they face up to a year in prison if convicted.
The junta has passed a special law banning campaigning either for or against the charter — although generally only those who push for a “no” vote have found themselves arrested.
Last month police even charged two eight-year-old girls for ripping down voter lists.
Critics say the new charter will straitjacket democracy with clauses calling for a fully-appointed senate and unelected premier — both of which could help the military elite keep its allies in power.
The controversial charter has even created rare common ground between rival political camps.
Ousted premier Yingluck today reiterated on social media her support for a no vote.
Last week Abhisit Vejjajiva, leader of the Democrat Party and a staunch Shinawatra opponent, also said he is against the charter.
Predicting the turnout or the outcome of the vote is difficult. Thai polling data is notoriously unreliable and exit polls are banned on the day.
Analysts believe a low turnout would make a “yes” vote more likely.