BANGKOK (REUTERS) - A Thai student activist detained for campaigning against a military-backed constitution and in the second week of a hunger strike will be released on bail on Friday, his lawyers said.

Voters overwhelmingly approved the constitution backed by Thailand's ruling junta in an Aug 7 referendum, paving the way for a general election in 2017.

Critics say the constitution will stifle democracy and entrench military influence in politics.

The military government prevented opponents from campaigning against the charter before the vote and the Election Commission introduced a law criminalising any such activity.

Jatupat Boonpattararaksa, a student at Khon Kaen University in the country's northeast, was detained on Aug. 6 for handing out "vote no" leaflets.

He went on hunger strike after he was detained and faces charges of violating the ban on campaigning.

Human Rights Watch called this week for his release and said he should be given access to medical treatment after he fainted on Monday. "We're bailing him out today because we want him to stop the hunger strike and take care of his health. But we don't know yet if he will stop," said Jatupat's mother, Prim Boonpattararaksa, who is also a lawyer and is working on his case.

Another lawyer working on the case, Anon Nampa, said Jatupat would be released in the evening.

As many as 195 people have been arrested on charges related to the constitution and campaigning ahead of the referendum, according to the group Thai Lawyers for Human Rights.

Thailand should "immediately drop all charges against political activists" and release those jailed for opposing the constitution, Ravina Shamdasani, spokeswoman for the UN High Commissioner for Human Rights, said in a statement.