A Cambodian court has jailed a 70-year-old barber for seven months over a violation of the country's royal insult law, the first such conviction since the law was adopted this year.

A court found Ban Samphy, 70, a member of the dissolved opposition Cambodia National Rescue Party (CNRP), guilty on Thursday after he shared a Facebook post about King Norodom Sihamoni in May, his daughter, Ang Vongpheak, 45, said.

"He was sentenced to a year in prison for insulting the king but only seven months will be enforced," Yin Srang, a spokesman for the court in the northern province of Siem Reap, told Reuters. He did not elaborate.

In February, Cambodia's parliament unanimously adopted the law forbidding insults to the monarchy. Rights groups expressed concern at the time that the law, similar to one in neighboring Thailand, could be used against critics of the government.

Last year, the Supreme Court dissolved the opposition CNRP at the government's request. It was found guilty of plotting to take power with the help of the United States- an accusation the party has denied.

In July, the ruling party Cambodian People's Party (CPP) of Prime Minister Hun Sen won a general election that critics said was flawed because of a lack of a credible opposition, among other factors.

Ang Vongpheak expressed disappointment at Thursday's verdict.

"I'm not happy with the court decision but I don't know what we can do," she said.