Oai, 36, was taken into custody by plainclothes officers in central Vietnam's Nghe An province on Jan. 19 for "resisting persons on duty" after authorities accused him of violating the terms of a house arrest order he received in 2015 for having ties to the outlawed Viet Tan pro-democracy organization.
A relative of Oai's, who spoke to RFA's Vietnamese Service on condition of anonymity, said authorities had recently provided the family with a court date, but little else.
"We haven't got any announcement from the court yet, so we don't know anything in detail," said the relative.
"We only know that the trial will be on Aug. 21, and nothing more."
Oai was among a group of 14 Catholic and Protestant youths arrested in August 2011 as part of a crackdown on activists with ties to religious organizations, anti-China protests, environmental advocacy, and citizen journalism, and had been held at a detention center in Hanoi.
He was sentenced to four years in prison and three years of probation for attempting to overthrow the government or joining organizations with the "intent" to do so under Article 79 of Vietnam's Penal Code, and returned to his home in August 2015 on completing the jail term.
Oai has maintained his innocence, saying he only spoke out to demand rights for the people of Vietnam, according to the country's constitution and laws.
His relative said Friday that the family is angered over his recent arrest and believes the charges against him are without merit.
"Our family can't accept the accusations, because he didn't do anything that would constitute a 'violation of house arrest,'" he said.
"Furthermore, the police came to his house without uniforms, pretending to be thugs. Oai didn't welcome them and challenged them, but that is reasonable because they were wearing street clothes ... so he can't be charged for 'resisting persons on duty.'"
The relative said that the arrest did not follow procedure, noting that the officers never presented a warrant when they entered Oai's home.
"All they did was beat him up and then took him away--that's why we are so upset."
In March, Oai's wife Linh Chau told RFA that she was two months pregnant and dealing with health issues when he was arrested that had led her to be hospitalized several times since then.
While Chau said life had become significantly tougher for their family since Oai's arrest, she welcomed support from people she said believe in his work.
Crackdown on dissent
At the end of last month, authorities in Vietnam arrested four members of a prodemocracy group on charges of attempting to topple the country's one-party state, drawing condemnation from their organization and international rights campaigners who demanded their unconditional release.
The four men--all members of the online group Brotherhood for Democracy--were charged under Article 79 and could face the death penalty if convicted.
Their arrests followed the conviction for "conducting propaganda against the state" under Article 88 in July of prominent activist Tran Thi Nga, 40, and in June of 38-year-old blogger Nguyen Ngoc Nhu Quynh, also known as Mother Mushroom (Me Nam), under the same charges.
The women were sentenced to nine and 10 years in prison, respectively.
Rights groups, the United Nations' Human Rights Commission, and several governments have demanded their release, saying the two were convicted on vaguely worded charges.
Communist Vietnam, where all media are state-controlled, does not tolerate dissent, and rights groups identify Article 79 and Article 88 as among a set of vague provisions that authorities have used to detain dozens of writers and bloggers.
Reported by RFA's Vietnamese Service. Translated by Emily Peyman. Written in English by Joshua Lipes.
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