The Ministry of Public Security said he had raised funds for anti-state activities,joined anti-Vietnam protests in Australia and recruited members for Viet Tan.
While primarily US-based,Viet Tan has members in Australia as well. The United Nations has described them as"a peaceful organisation advocating for democratic reform"in Vietnam.
The Australian director of Human Rights Watch,Elaine Pearson,said that back in the 1980s,Viet Tan overtly supported resistance to the socialist regime in Vietnam but"they haven't done that for a long time".
"They operate openly in the US,in Australia,and certainly they are not a terrorist group. For someone to be prosecuted for associating with them - these people are not ISIS. These people promote human rights and democracy in Vietnam,"she said.
"They have members in Sydney and Melbourne,for example,they are active in Australia but it's in the US where they are much more active."
In the lead up to Chau's trial,Australia's Department of Foreign Affairs would say only that it was"providing consular assistance to an Australian man detained in Vietnam".