At least eight people have died in the conflict, which broke out earlier this month, and thousands have been displaced.
The two sides have disagreed on everything, from who fired first and where troops were stationed to how best to end the standoff.
But Indonesian Foreign Minister Marty Natalegawa said after a meeting with the 10-member Association of Southeast Asian Nations that Cambodia and Thailand agreed to a proposal to send up to 40 military and civilian observers to the remote, mountainous area.
The unarmed observers — all from Indonesia — will “observe the commitment by both sides to avoid further armed clashes” and provide accurate and impartial reports about complaints of violations from both sides of the borders, he told reporters after the 90-minute meeting.
They will report to both ASEAN and the UN Security Council.
The conflict — which involved exchanges of small arms, mortars and artillery fire — is rooted in a decades-old border dispute near Preah Vihear temple and has fueled nationalist passions on both sides.
The monument was built between the 9th and 11th centuries and sits atop a 525-meter cliff. While awarded to Cambodia by the World Court in 1962, sovereignty over adjacent areas has never been clearly resolved.
Skirmishes have erupted several times since 2008, when Preah Vihear was given UN World Heritage status, but soldiers and locals say none has been as violent as the latest clash.
The UN Security Council expressed “grave concern” Monday and gave strong backing to the efforts of ASEAN — which usually refrains from interfering in the internal affairs of member states — to help end the dispute.
The regional grouping last deployed observers in 2005 — when it helped oversee a peace deal between rebels and government troops in Indonesia’s westernmost province of Aceh — and has also participated in conflicts in East Timor and the southern Philippines.
Natalegawa made clear on Tuesday that Southeast Asian countries were again ready to step in.
“I would like to make it absolutely clear that ... the option of conflict, the option of use of force, is not meant to be on the table,” he said ahead of talks, adding “we are waging peace” not war “so that no more guns and artilleries make a sound in our region.”
The border has been tense but quiet in recent days.
Earlier on Tuesday, Cambodian Prime Minister Hun Sen told university graduates in Phnom Penh monitors would be welcome to all areas inside the border, from the front lines to military camps and ammunition warehouses.
“They can inspect wherever and whenever they want.”
While he has tried hard to shift the debate to an international stage, asking for both UN peacekeepers and ASEAN monitors, his Thai counterpart, Abhisit Vejjajiva, has pressed hard for a bilateral solution.
ASEAN is comprised of Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand and Vietnam.
