Um Sam An, a member of the opposition National Rescue Party, was charged Tuesday after being arrested in Siem Reap province following a trip abroad.

The lawmaker had been critical of premier Hun Sen's use of contested maps to demarcate the border between Cambodia and Vietnam, and said the government was conceding land to its neighbor.

Now, Um Sam An faces up to five years in prison after being charged with incitement to commit a criminal act and inciting prejudice against another country. An Interior Ministry spokesman told AFP news agency that Um Sam An had incited "racism between Cambodia and Vietnam."

Fraught relations

The two countries have a long, fraught history with each other, having engaged in a decade-long conflict that began when Vietnam invaded Cambodia in 1979. Anti-Vietnamese sentiment remains strong in Cambodia to this day.

While Cambodia is a democracy, Hun Sen, who's been in power for three decades, is known for his authoritarian tactics. In a speech broadcast on state-run radio, the premier threatened that anyone who brought up the issue of contested maps "must be handcuffed."

One of Um Sam An's colleagues from the National Rescue Party is also facing charges for having criticized the government's border policy.

Fractured politics

The opposition party did surprisingly well in the 2013 general election, and Hun Sen eventually reached a political truce with the party after it boycotted parliament following the beating of two of its members by pro-government protesters.

The National Rescue Party criticized the arrest of Um Sam An, calling it a violation of parliamentary immunity, but the government defended his detention as legal.

Um Sam An remains in detention until his trial, which has yet to be scheduled.

blc/ j (AFP, AP)