A Thai politician has appealed for Australian help after being detained by Thailand's military government, which may force him to attend a week-long "re-education" camp.

Watana Muangsook was once Thailand's commerce minister and is a member of the Pheu Thai party, aligned with the so-called Red Shirt faction of politics.

He was summoned to a military base in Bangkok yesterday and has been detained since then.

Mr Watana angered the military junta by advocating a no vote in an upcoming referendum, which will choose whether to adopt a new constitution and a new Senate, in which members are appointed by the military.

While the military government has conducted many "attitude adjustments" since taking power two years ago, Mr Watana may be the first to be sent to a week-long "re-education camp".

He has appealed to Australian Foreign Minister Julie Bishop to monitor any abuse of power in Thailand.

"I am strongly dissatisfied with the arrest warrant issued by the military in a so-called 'attitude adjustment', obviously a tool to intimidate and suppress the opposition," he wrote in a letter sent to Ms Bishop and obtained by the ABC.

"I would like to take this opportunity to [appeal] to the international community and the human-rights-related organisations to please help check and examine the tendency for power abuse of the NCPO," he wrote, using the military government's official name, the National Council for Peace and Order.

The ABC has contacted Ms Bishop's office for comment.

Watana Muangsook also sent the letter to UN General Secretary Ban Ki-moon and to diplomats in Bangkok.

The referendum you can't (publicly) say 'no' to

Since the coup in May 2014, the military has ruled the country under an interim constitution.

In August, Thailand will hold a referendum to decide the shape of its political future.

The military Government has forbidden any public campaigning for or against the new political structure.

"You can like or dislike [the charter] but don't express it [to the public] and keep it inside your head," said a deputy Prime Minister Prawit Wonsuwan, according to The Nation newspaper.

He was responding to academics who wore "Vote No" t-shirts during a public lecture opposing the new constitution.

However, comments from another deputy Prime Minister, Wissanu Krea-ngam, appeared to support the academics' right to discuss the referendum options.

He told the Bangkok Post newspaper the academics' commentary is "still under the law" and offered "reasonable opinions without a political agenda".

The military Government has promised national elections next year, but critics say the addition of an appointed Senate would give the junta ongoing power over any elected government.