Eight Chiang Mai politicians will be detained for seven days and then be charged in the military court with sedition and spreading false information on the draft charter through letters, Deputy Prime Minister Prawit Wongsuwon said on Thursday.
The week-long detention period was ordered by the National Council for Peace and Order (NCPO).
The Pheu Thai Party politicians are accused of disseminating thousands of letter spreading false information to households in the North.
Gen Prawit, who is defence minister, denied claims the NCPO was persecuting its political opponents ahead of the charter referendum on Aug 7.
The NCPO had not expected the incident in Chiang Mai province, but since it occurred there authorities had to take legal action on the evidence to hand, he said.
Several of the targeted people are of the politically influential and very wealthy Buranupakorn family, a major supporter of the Pheu Thai Party in Chiang Mai, which is the party's stronghold.
They include Tasanee Buranupakorn, a former Chiang Mai MP and vice-president of the Chiang Mai provincial administrative organisation, her younger sister, and her uncle Boonlert Buranupakorn, whom Prime Minister Prayut Chan-o-cha earlier suspended from the position of president of the Chiang Mai provincial administrative organisation.
The NCPO did not pick on any particular family or politician in Chiang Mai, but was taking action in accordance with available evidence, Gen Prawit said.
Police raided the family's property on Saturday and said they found letters that wrongfully claimed the draft charter would terminate the government's 30-baht healthcare scheme, monthly payments to the elderly and free schooling.
The detainees were taken to the 11th Military Circle in Dusit district, Bangkok, on Wednesday.
