PHNOM PENH, June 2, 2025 (BSS/AFP) - Cambodia will file a complaint with the International Court of Justice (ICJ) over border disputes with Thailand, Prime Minister Hun Manet said Monday, after a Cambodian soldier was killed in a recent frontier clash.

"Cambodia hopes that the Thai side will agree with Cambodia to jointly bring these issues to the International Court of Justice... to prevent armed confrontation again over border uncertainty," Hun Manet said during a meeting between MPs and senators.

Military clashes between the Southeast Asian neighbours erupted in 2008 and have led to several years of sporadic violence, resulting in at least 28 deaths.

The most recent occurred Wednesday, when a Cambodian soldier was killed in a location known as the Emerald Triangle -- a joint border area between Cambodia, Thailand and Laos.

The day after, Cambodia's foreign ministry sent a letter to the Thai embassy in Phnom Penh demanding "an immediate and thorough investigation" into the "unprovoked attack".

Describing the incident as "a violation of Cambodian sovereignty", Phnom Penh said it remained committed to resolving the issue through "peaceful and diplomatic avenues".

Prime Minister Hun Manet said that even if the Thai side did not agree on bringing the issue to the ICJ, Cambodia would still file the complaint.

He added that the border dispute was being "incited by small extremist groups in both countries", which could lead to further clashes.

Thailand's ministry of foreign affairs did not immediately respond to a request for comment from AFP.

Cambodia's military had said they were attacked first in Wednesday's incident, while the Thai side said their soldiers were responding to gunshots.

The Thai and Cambodian militaries met the following day, agreeing to ease tensions.

Thailand says a Joint Boundary Committee will meet in the next two weeks to resolve the issue.

The Emerald Triangle is among the areas that will be named in the ICJ complaint, Hun Manet said.

Another is Ta Moan Thom Temple, the backdrop for a video posted on social media earlier this year showing a woman singing a patriotic Khmer song which led to Bangkok lodging a formal protest to Phnom Penh.

Cambodia and Thailand have long been at odds over their more than 800-kilometre-long (500-mile) border, which was largely drawn during the French occupation of Indochina.

The 2008 military clashes erupted over a patch of land next to Preah Vihear Temple, a 900-year-old structure near their shared border.

This led to several years of sporadic violence before the International Court of Justice ruled the disputed area belonged to Cambodia.