Northeastern activists have denounced the high costs of drafting the new constitution, calling for an early election so people can vote in the government that shapes their laws.
Lertsak Kumkongsak, a Bangkok-based Northeastern conservationist, said the military's attempt to write a new constitution while the country is still under martial law will only aggravate dissent and divisions in society.
"Spending more than 250 million baht on the controversial mission will not be worthwhile. It will actually be counter-productive, because those who think differently remain suppressed. Why don't they allow an elected government to undertake the mission?" he said.
Mr Lertsak is one of a dozen Northeastern civil society activists who has been critical of the coup and subsequent reform and charter-drafting efforts.
Activists from 12 organisations were summoned by the military and asked not to make any critical remarks against the government after signing their first joint protest statement more than a month ago.
The group issued another statement over the weekend criticising the coup and the ongoing reform process.
They said the May 22 coup had not only destroyed democracy but also civil society, since some organisations have joined the military-led reform and charter drafting work.
But even within the temporary constitution, there is no guarantee the views of the National Reform Council will be taken into account, they said.
The basic rights of the people continue to be suppressed, they added. This includes the right to assemble to air grievances over falling rice and rubber prices, and the right to freedom of expression.
Government restrictions on those who think differently from them has undermined the bargaining power of grassroots movements, while favouring capitalists and elites in Thai society, the group said.
The activists called for polls to be held by early next year to allow an elected government to preside over the drafting of the constitution and reform agenda within three years.