BANGKOK (Reuters) - A Thai court on Monday released on bail four people detained for campaigning against a military-backed draft charter, their lawyer said.

The arrests on Sunday were the latest by authorities in the lead-up to a referendum next month.

The Aug. 7 referendum will be the first time Thais go to the polls since the military seized power in a bloodless coup in May 2014. The ruling junta has said the referendum will pave the way for an election next year.

Critics, including major political parties, say the constitution will enshrine a political role for the military and weaken civilian governments, worsening the turmoil that has hit Thai politics over the last decade.

The four were detained in Thailand's western Ratchaburi province on Sunday, said police, after their cars were searched and copies of booklets providing information on the constitution were found.

The group had violated a law that carries a 10-year jail term for campaigning in connection with the referendum.

"They violated the Referendum Act," said Police Captain Poom Klaklaew, a police investigator for the case.

A court in Ratchaburi released the four on bail of 140,000 baht ($3,986) each on Monday, Pawinee Chumsri, a lawyer for the group, told Reuters.

With less than a month to go before the referendum, the junta has taken what rights groups say is a hardline stance on any opposition to its plans and has banned all public discussion of the constitution.


Among those detained was a reporter from Thai online publication Prachatai, Taweesak Kerdpoka, who joined three activities to report on their activities.

"Police found a few copies of the booklet in his bag," said Kornkritch Somjittranukit, who works with Taweesak at Prachatai.

"He told them it was material for his news report, but they arrested him anyway."

Colonel Winthai Suvaree, a junta spokesman, said the arrests were a police matter.

"The police probably didn't know who was who when they detained the group," Winthai told Reuters. "They weren't out to target the journalist."

The latest arrests followed the release last week by a military court of seven activists detained in June for campaigning against the charter.

(Reporting by Amy Sawitta Lefevre, Panarat Thepgumpanat and Patpicha Tanakasempipat; Editing by Richard Borsuk)