Anson Wong was arrested in August 2010 at Kuala Lumpur's international airport while attempting to smuggle 95 endangered boa constrictors to Indonesia.
He was sentenced to five years in jail, but a Malaysian appeals court freed him in 2012, sparking an outcry.
Malaysian authorities had said in the wake of Wong's arrest that his licences for legitimate wildlife trading were revoked.
But, in an investigative report, Al Jazeera said Wong and his wife Cheah Bing Shee were believed to be trading albino pythons and other wildlife from their base in the northern Malaysian state of Penang.
More From This Section
The report, called "Return of the Lizard King" and aired late Thursday, said documents also revealed shell companies used by Wong to hide his activities.
Illegal trade in wildlife is thought to be worth at least USD 19 billion a year worldwide, according to conservation groups.
Outraged conservationists demanded action from the government and expressed shock over the lax attitude by the authorities for failing to monitor Wong.
"The 'Return of the Lizard King' raises so many doubts and questions about Malaysia's commitment to that fight. It is time we had some solid answers from government," Shenaaz Khan, an official with wildlife-trade monitoring network Traffic, said in a statement.
In Penang, Al Jazeera's Chao confronted Wong on camera, but he declined to comment.
Several of Wong's former associates also claimed that corrupt customs officials in Malaysia, Indonesia and Madagascar were helping to facilitate Wong's activities, the report said.
In a press release, Al Jazeera said Chao and his team worked with anti-trafficking groups to track Wong's Malaysian-based operation.