According to George Yeo, Singapore's foreign minister, Nyan Win told him during a pre-summit dinner on Sunday that under Myanmar law a political detainee can be held for a maximum period of only six years.
That timescale, in relation to Aung San Suu Kyi's detention, would expire within six months, he said.
"He told me that the six-year limit will come up in about half a year's time," Yeo told reporters on Sunday.
Asked whether that meant she could be freed, he said: "I am just repeating to you what he told me and I think that is not an inaccurate inference."
House arrest extended
In May, Myanmar's ruling military announced it was extending Aung San Suu Kyi's house arrest for another 12 months.
It is not clear how the foreign minister's suggestion that she could be freed affects that decision.
Aung San Suu Kyi has been held under house arrest or in Yangon's notorious Insein jail for most of the past 18 years.
Her party, the National League for Democracy, won a landslide victory in national elections held in 1990, but it was never allowed to take office.
During the Singapore summit, Asean leaders are due to release a report on the aftermath of Cyclone Nargis, which swept through Myanmar's Irrawaddy Delta in early May leaving more than 80,000 dead.
Myanmar's generals were widely criticised over their response to the storm and for blocking access to international relief groups in the crucial early days of the disaster.