The arrest came just days after a state visit from US Secretary of State Hillary Clinton.
Police say Beehive Radio operator Mam Sonando has been leading a secessionist movement, inciting people against the Cambodian government.
Meanwhile, China has built strong relationships across the region, in countries like Cambodia, which could divide Asean countries.
A senior State Department official said the talks will take place Friday on the sidelines of a conference in Cambodia.
Four ASEAN members - Brunei, Malaysia, the Philippines and Vietnam - claim overlapping parts of the South China Sea.
Patrick Devillers, who has been detained since his arrest in Phnom Penh on June 13, can return at his own request.
Asean leaders are expected to approve the declaration in a major summit in November.
The feeling from ASEAN officials was that Burma, should be rewarded.
Regional tensions have risen recently, with Vietnam and the Philippines accusing China of aggressive behavior in the sea.
US Secretary of State Hillary Clinton’s trip to the Asean Regional Forum in Phnom Penh next week will mark her second visit to Cambodia.
Interpol equipment linked to the database has been installed in Cambodia since June, officials said.
Secretary of State Hillary Clinton is scheduled to attend an Asean security forum this month.