Registration opened on September 1 and will close on November 9, with registration offices open only on weekdays.
The CNRP in a statement on Sunday called for Sokha’s immediate release and condemned the arrest of a lawmaker in violation of his constitutional immunity.
The U.S., and press freedom and human rights groups, strongly criticize Cambodia’s decision to shutdown and pressure civil society and media.
The announcement on Wednesday comes amid a broad crackdown on non-governmental groups and critical media outlets ahead of a crucial general election next year, rights groups have said.
Mam Sonando blamed a lack of funding for the party’s failure but added that he would continue to be active in politics by giving lectures and making radio appearances.
For some 15 years councilors have been forced to work out of a small area in a villager’s home.
The Sala Kam Reuk commune chief said the commune office is markedly busier than is was under the guardianship of his predecessor.
The opposition Cambodia National Rescue Party won 489 out of 1,646 commune chief positions in the June 4 election.
The letters ordered the groups to halt their activities and said the Situation Room was an unregistered organization and in breach of the law.
The political parties law was amended before the election to block people with criminal records from leading political parties.
The ruling Cambodian People’s Party won 1,156 seats to the CNRP’s 489, with one seat also won by the Khmer National United Party.
Morn Phalla told VOA Khmer he was unaware of any violence being reported during the election campaign, which he organized for the opposition.