phnom penh cambodian opposition leader kem sokha charge treason could face jail term 15 30 years convict court say tuesday kem sokha arrest sunday escalate crackdown critics prime minister hun sen government accuse opposition leader plot unite state undermine southeast asian country trials senior political figure recent years result convictions international right group question whether proceed kem sokha would fair charge collude foreigners article 443 cambodia penal code phnom penh municipal court say statement act secret collusion foreigners act treason add evidence government present video kem sokha 2013 tell supporters cambodia national rescue party cnrp american support advice political strategy win power one opposition leader lawyers pheng heng say appear video clip crime legal procedure wrong charge correct say talk elections multi-party democratic way arrest kem sokha grow pressure independent media right group draw condemnation unite state western countries raise doubt whether general election next year fair hun sen one asia long serve rulers support china make one close regional ally provide billions dollars infrastructure loan next year election could represent great challenge hun sen rule cambodian people party cpp three decades rule critics accuse try shut opposition advance pro-government website fresh news say could arrest officials opposition party case government rule cpp manufacture treason charge kem sokha political purpose aim try knock political opposition ring 2018 electoral contest even begin say phil robertson deputy asia director new york-based human right watch kingsley abott senior international legal adviser southeast asia geneva-based international committee jurists say allegations kem sokha hallmarks politically motivate absence independent impartial prosecution judiciary make delivery fair trial impossible political case say kem sokha sentence five months jail last september fail appear court connection case two party colleagues late pardon hun sen request avoid prison occasion take refuge party headquarter kem sokha predecessor party leader sam rainsy find guilty defamation absentia live france avoid conviction say politically motivate cambodia charge opposition leader treason