Eight land activists put in prison last month after a swift trial say they will hold a hunger strike if they are not released.
In a hand-written letter from Prey Sar prison, the activists say they were improperly tried by Phnom Penh Municipal Court.
Among those threatening the hunger strike is renowned activist Tep Vanny, who was awarded for her work by Washington-based Vital Voices last year.
Her husband, Ou Kong Chea, told VOA Khmer he fears for her wellbeing and will seek to visit her in jail this week.
The eight activists were part of a roundup in November for street protests against city officials and a development project at Boeung Kak lake, which forced the evictions of thousands of families. It also meant the filling of the lake, which critics say has created a flooding problem for residents.
Rights groups have condemned the arrests and almost immediate sentencing of the activists, to one year in prison.
Lawyers for the activists say they have appealed the case but it has not moved to the Appeals Court. Court officials could not be reached for comment Monday.