Southeast Asia may appear relatively stable on the surface, but beneath that calm are a series of unresolved territorial and maritime disputes that continue to test the region’s diplomacy—and raise the risk of sudden military confrontations.
A recent analysis by The Diplomat highlights how Southeast Asia’s territorial disputes extend far beyond the internationally prominent South China Sea. Several long-running land and maritime claims remain unsettled, creating potential flashpoints that could deteriorate rapidly if nationalist politics, military deployments or a border incident push tensions beyond diplomatic control.
The warning comes at a particularly sensitive moment for the region. The 2025 Thailand-Cambodia fighting demonstrated that a dispute that had simmered for years could once again turn violent, while confrontations between China and the Philippines in the South China Sea have continued into 2026.
Thailand-Cambodia: The Warning Southeast Asia Cannot Ignore
The most immediate reminder of the dangers surrounding unresolved borders is the Thailand-Cambodia dispute.
The two countries experienced serious fighting in 2025, with clashes involving artillery and airstrikes. Reuters reported in July 2026 that nearly 150 people were killed and around 300,000 displaced during the fighting. Although ceasefires were reached, troops remain deployed along portions of the frontier.
Thailand has since begun constructing sections of a permanent border fence. The Thai military said in July that a 1.3-kilometer reinforced section had been completed, with plans for more than seven kilometers of additional fencing in selected areas along the 817-kilometer frontier.
The physical fortification is significant because it illustrates how an unresolved territorial dispute can continue influencing security policy even after active fighting stops.
The two governments have also pursued diplomatic mechanisms. Cambodia initiated a compulsory conciliation process under the United Nations Convention on the Law of the Sea (UNCLOS) over a separate maritime boundary dispute, while Thailand agreed to participate in the process.
That combination—military preparedness alongside diplomatic negotiations—underscores the fragility of the situation.
South China Sea: The Region’s Most Dangerous Maritime Flashpoint
If the Thailand-Cambodia frontier demonstrates the danger of land disputes, the South China Sea represents the far more complicated maritime challenge.
China, the Philippines, Vietnam, Malaysia, Brunei and Taiwan have overlapping claims in the strategically important waters. The dispute is particularly sensitive because the South China Sea is a major commercial and energy route and contains potentially significant natural resources.
Tensions between Beijing and Manila have remained particularly intense.
In July 2026, China and the Philippines traded accusations following a confrontation near Second Thomas Shoal. Manila alleged that Chinese Coast Guard personnel struck a Philippine navy sailor and damaged a Philippine rubber boat, while Beijing accused the Philippines of provoking the encounter.
Days later, the Philippines accused China’s Coast Guard of using water cannon against Philippine government vessels near Scarborough Shoal, describing it as another confrontation in a rapidly escalating week. China said it had taken what it described as legal control measures against Philippine vessels.
China subsequently conducted military and coast guard patrols around the disputed shoal, further demonstrating how quickly maritime confrontations can acquire a military dimension.
The United States has also remained closely involved. Washington has repeatedly reaffirmed its treaty commitment to the Philippines, while Philippine, U.S. and Japanese forces conducted maritime exercises in July amid the renewed tensions.
Manila and Beijing Are Still Talking
Yet the picture is not simply one of inevitable confrontation.
Philippine President Ferdinand Marcos Jr. said in August that joint oil and gas exploration with China remains a possibility despite the countries’ continuing territorial disagreements.
Marcos stressed that Manila had not surrendered its sovereign rights, while both sides continued discussions over a potential framework for energy cooperation.
That distinction is important.
Territorial disputes can coexist with economic cooperation. In fact, governments often maintain diplomatic and commercial channels precisely because completely severing relations could make escalation more likely.
The challenge is keeping those channels open when encounters at sea, domestic political pressure and military deployments continue to increase.
Why These Disputes Matter Beyond Southeast Asia
The danger posed by territorial disputes is not limited to the countries directly involved.
Southeast Asia sits at the intersection of major geopolitical powers. The United States and China are competing for strategic influence, while countries such as Japan, Australia and India have strengthened their security relationships with regional states.
At an August forum in Manila, U.S. Deputy Defense Secretary Elbridge Colby urged Asian allies and partners to increase their own defense investments, arguing that regional deterrence should not depend exclusively on American military power. He also reaffirmed Washington’s commitment to Asia and specifically highlighted the importance of the Philippines and other Southeast Asian partners.
That means a localized territorial incident could potentially acquire much wider strategic consequences if treaty allies or major powers become involved.
The Other Disputes Beneath the Radar
The South China Sea and Thailand-Cambodia border are only part of the picture.
Southeast Asia has numerous unresolved maritime boundaries, overlapping claims and areas where borders were never fully demarcated.
Among them are competing maritime interests involving Malaysia, Vietnam and the Philippines. These disputes generally receive less international attention than the China-Philippines confrontation, partly because the governments involved have often relied on negotiations and avoided direct military escalation.
That relative calm, however, should not be confused with permanent resolution.
The region’s experience shows that disputes can remain dormant for years before suddenly becoming politically explosive.
ASEAN Faces Its Biggest Test
The Association of Southeast Asian Nations remains central to the region’s effort to prevent disputes from becoming open conflicts.
But ASEAN faces an inherent challenge: its members have different national interests, security relationships and positions on territorial disputes.
The bloc has demonstrated that it can facilitate dialogue, including efforts surrounding Thailand and Cambodia. Yet its consensus-based approach can make decisive collective action difficult when member states themselves have competing interests.
The situation is even more complicated in the South China Sea, where ASEAN must negotiate collectively with China while several ASEAN members are themselves claimants.
The bloc has continued working toward a South China Sea Code of Conduct, but negotiations have taken years.
The Real Danger May Be an Accident
The biggest threat may not necessarily be a government deliberately deciding to start a war.
It could be an accident.
A collision between vessels. A dangerous maneuver. A miscalculated military response. A border patrol confrontation. A domestic political crisis that turns a relatively small incident into a nationalist cause.
The recent China-Philippines confrontations demonstrate how quickly maritime encounters can trigger diplomatic protests and military signaling.
Thailand and Cambodia provide an even more serious warning: unresolved territorial questions can remain dormant for years before erupting into deadly fighting.
Southeast Asia Is Not Destined for War
Calling these disputes “wars in waiting” captures the potential danger, but it should not be interpreted as a prediction that major wars are inevitable.
The opposite may be closer to the truth.
The fact that governments continue negotiations, pursue arbitration, maintain diplomatic channels and participate in regional institutions shows that there are still mechanisms capable of containing disputes.
The problem is that those mechanisms are being tested at the same time that military capabilities are expanding and geopolitical competition is intensifying.
For Southeast Asia, the critical question is therefore not simply which border dispute could become a war.
It is whether ASEAN and the region’s major powers can prevent the next confrontation from becoming the spark that nobody intended to ignite.
And with territorial claims still unresolved from the Mekong to the South China Sea, the next crisis may not come from the flashpoint the world is watching today—but from one that has been quietly building outside the headlines.
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