The past year has taken its toll on Sydney woman Trang Chau and her family.

Key points: Chau faces the prospect of 11 more years in a Vietnamese jail cell

Chau faces the prospect of 11 more years in a Vietnamese jail cell Hanoi alleges he committed "terrorist activities" against the state

Hanoi alleges he committed "terrorist activities" against the state His family are fighting for his freedom to return to Australia

"[I'm] very sad and very stressed," she told the ABC.

It's been a full year since she last saw or even spoke to her husband, Van Kham Chau, who was whisked into Vietnamese police custody on January 15 last year.

In a trial lasting less than five hours and condemned as a "sham", the Australian citizen was sentenced to 12 years behind bars in Ho Chi Minh City.

Human rights groups have likened the lengthy prison term to a "death sentence" for the retired baker.

"He's 70 years old now — he has many illnesses, like high cholesterol, high blood pressure and issues affecting his eyes, so I'm very worried," Ms Chau said.

"When he was sentenced, I felt very heavy. I was speechless, I didn't know what to do."

"He can't stay in prison for long."

Chau's son Daniel and wife Trang are fighting to bring him home. ( ABC News: Mazoe Ford )

Ms Chau has been able to communicate with her husband only through letters scanned and passed through the hands of consular and prison officials.

Last year, Chau wrote to her: "My health is good, but my spirit is declining … I'm waiting for the day I can come home."

He was convicted of "terrorist activities" against the state and sentenced last year alongside Vietnamese men Nguyen Van Vien and Tran Van Quyen.

Chau was sentenced to 12 years in jail for "terrorism to oppose the people's administration" in a trial lasting less than five hours. ( AP: Nguyen Thanh Chung/VNA )

Chau lodged an appeal against his conviction in November, but the Chau family's Australian-based lawyer Dan Phuong Nguyen said there had been no legal developments since.

Chau is an active member of activist group Viet Tan — a group that is considered a terrorist organisation by Hanoi — and prior to trial he was accused of entering Vietnam on false documents.

The pro-democracy group has a history of resistance aimed at toppling the communist government stemming from the 1980s, but in recent decades has maintained it is "committed to peaceful, nonviolent struggle," according to Human Rights Watch.

His son Daniel has said it's "ludicrous" that his father, who arrived in Australia as a refugee by boat in the 1980s, is considered a terrorist.

"My dad's in his 70s. He's passionate, but he alone isn't going to cause violence or anything like that," Daniel told the ABC last year.

His youngest son Dennis has said his father's activism was motivated by the lack of fundamental freedoms in the country of his birth.

"It feels like there's a sort of hole missing that I'm not able to give him updates on what's happening in my life while I wait on his," Dennis told the ABC on the one-year anniversary of his father's arrest.

"It still feels very strange and I don't think I've accepted it."

He is planning to head to Geneva for a human rights convention in February to raise awareness about his father's case.

'No justice in this'

Amnesty International has said Chau, as a political prisoner, is not alone. The human rights group says there are at least 128 prisoners of conscience in Vietnam as of March last year.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 28 seconds 1 m 28 s Some in the Vietnamese community rallied in Canberra in November to bring imprisoned Australian Van Kham Chau home.

Chau's family and members of the Vietnamese community have made repeated appeals to Australian Prime Minister Scott Morrison to help bring Chau home.

Melbourne social worker Hong Vo, a friend and fellow member of Viet Tan, was arrested for protesting in Vietnam in 2010, but after lobbying from the Australian Government, she was released after 10 days.

Melbourne social worker and Viet Tan member Hong Vo fears for Chau's health and mental wellbeing. ( ABC News: Erin Handley )

She said watching the result of Chau's trial, who she described as "a very kind father" and regarded as a mentor, was distressing.

"I found no justice in this, because the Vietnamese Government has no evidence to accuse him of terrorism," she said.

She feared he would be struggling mentally and physically with the long incarceration, and recalled being "interrogated, intimidated and brainwashed" every day during her brief detention, which left her feeling "powerless".

She said she had been heartened by senators during a recent campaign in Canberra to advocate for his release, and by the support from the broader Australian community who were worried about his case.

"It is the duty of the Government to protect justice and to protect citizens from unfair and unjust trials over there," she said.

"I hope the Government is working hard to bring him home soon."

'I do hold hope'

When asked to comment, Vietnam's Foreign Ministry re-sent a previous statement in which they said Chau's trial "proceeded in an open and transparent manner … ensuring in full the rights of the defendants".

"Viet Tan is a terrorist group that has made multiple attempts to infiltrate people and arms into Vietnam with the aim to sabotage, riot, incite hatred among Vietnamese nations and cause social instability," it said.

"Viet Tan continues to conduct activities to overthrow the State of Vietnam, smuggle people into Vietnam to sabotage, provoke people to disturb public disorder, oppose law enforcement officers and damage properties, broadcast propaganda to falsify the guidelines and policy of the State of Vietnam," they said.

But those allegations have been rubbished by rights groups and are disputed by Carl Thayer, emeritus professor at the defence force academy at UNSW, who has told the ABC Viet Tan's members include doctors and lawyers in Australia and the US who today advocate democracy through words, not weapons.

Australia's Foreign Minister Marise Payne said in a statement that "it would be inappropriate and not in Mr Chau's best interests to comment while legal processes remain available", and that "the Department of Foreign Affairs and Trade continues to provide ongoing consular assistance".

In a letter from prison, Chau reminded his son Daniel and his wife Trang to trim the okra trees in the family's garden. ( ABC News: Mazoe Ford )

For Ms Chau, who has endured the past year without her husband by her side and is facing the prospect of 11 more, action from the Australian Government is vital.

"Of course they should help him, he's an Australian citizen — they should help him," she said.

"I do hold hope. I've been to Canberra and spoken to [politicians] there, people of high standing, and they're promising to intervene."