Sombath Somphone was detained by police on the evening of December 15 when his Jeep was stopped at a police post on the road to the home of he and his wife, Ng Shwee Shui Meng.
Security camera footage shows a motorcyclist then entering the post and leaving about 15 minutes later to drive away the jeep.
Soon after, the footage shows two men escorting Mr Sombath into a waiting truck. Mr Sombath has not been seen since.
A statement from the authorities says that "it may be possible Mr. Sombath has been kidnapped perhaps because of a personal conflict or a conflict in business or some other reasons".
The statement says that: "at this stage the authorities are not in a position to say exactly what has actually happened, why Mr. Sombath has gone missing and who have been involved in the incidence."
Mr Sombath's wife, Ng Shwee Shui Meng, told Radio Australia's Connect Asia she has appealed to the Lao government to investigate.
However, she says she has not heard any information from the police or the Ministry of Public Security, despite writing two letters to the Ministry.
"I am completely surprised and I have no idea whatsoever the reasons why he should be held," she said.
"He is a upright citizen, he has always worked closely on development issues, working directly with issues that are relevant, on social issues."
Ms Shui Meng says she doesn't believe her husband's role on the National Organising Committee of the Asia-Europe People's Forum could have annoyed the government, as the forum was held "in cooperation with the government, every step of the way."
She says she hopes appeals from the US State Department, the UN and other NGO's to the Laos Ministry of Foreign Affairs will encourage them to release him.
"We hope that the government will consider this carefully and to release information about his whereabouts, and then to release him and ensure his safety," she said.
Ms Shui Meng says her husband recently stepped down from his role as director of the Participatory Development Training Centre to concentrate on writing and other interests.
"He has worked very hard for the last 30 years and he just wanted to retire," she said.