Abney’s injury in the attack prompted an FBI investigation that was ultimately abandoned.
Chea Vichea was a powerful labor leader able to amass large rallies, his killers have never been brought to justice.
At least 20 people, including some police and military police were injured, and at least 12 people were arrested.
Thailand forcibly returned more than 100,000 Cambodians last year.
Chhoung Chu Ngy briefly disappeared on Thursday last week, but he appeared shaken before a press conference on Friday.
Across Asean there is a diversity of political systems and leadership, as well as wide economic gaps.
In a meeting this week both foreign ministers said they would speed up negotiations over joint development in offshore blocs.
The Thai foreign minister made his request on an official visit to Cambodia and suggested consideration of a royal pardon.
Recently, Prime Minister Hun Sen has called for the nullification of land certificates in protected natural areas in Cambodia.
Over the year, nearly 110,000 people sat in on court proceedings to observe the trial process, Huy Vannak said.
The draft law has come under continued criticism from international and local NGOs, who say it will stymie their work.
The two appeared before the Court of Appeals on Wednesday, withdrawing their appeal without explanation.