A Cambodian-American dissident who has been labelled a terrorist by the government will face charges of treason at the Phnom Penh Municipal Court later this month.

Sourn Serey Ratha, the self-exiled leader of the Khmer People Power Movement (KPPM), will be put on trial on September 18 to face charges ranging from “treason” to “incitement to commit a crime”, according to a court summons obtained this week.

Defence lawyer Sok Sam Oeun said the court had “combined two cases” against Serey Ratha; one involving T-shirts bearing anti-election slogans and the other regarding flowers and leaflets that allegedly encouraged a military coup.

Serey Ratha, who is currently in Thailand meeting with members of the KPPM, said he will not attend the trial. The dissident added that he will attempt to register a political party, the Khmer People Power Party, ahead of the court date.

“Paperwork will be finished this week and my team will [submit it] . . . before 15th September,” he said by email.