ASEAN member states today stand at a genuine maritime inflection point. What were once navies designed primarily for coastal patrol, law enforcement, and search-and-rescue are being transformed into more capable, multidimensional sea forces. This shift is not simply a matter of prestige or military modernisation for its own sake. It reflects a deeper understanding of the maritime domain as central to sovereignty, national survival, and regional stability.
For Southeast Asia, maritime security matters as much for economic resilience and resource protection as it does for traditional defence. The region’s governments now recognise that without capable navies, the maritime foundations of their national interests remain vulnerable.
Maritime Disputes and the Return of Naval Deterrence
The first and most visible driver of this transformation is the persistence, and in some cases intensification, of maritime territorial disputes. Nowhere is this more evident than in the South China Sea, where competing claims, coercive maritime militia tactics, and increasingly frequent confrontations at sea have prompted several ASEAN states to invest in stronger naval deterrence. The Philippines has moved decisively in this direction. Manila is acquiring new corvettes from South Korea, enhancing its surface fleet and fielding the BrahMos anti-ship missile system - its strongest maritime deterrent to date. These steps signal a national shift from reactive defence to forward-leaning deterrence.
Malaysia is also recalibrating its naval posture. Putrajaya’s order for three Turkish-built Ada-class warships, to be deployed near the strategically sensitive waters off Sarawak in Borneo, demonstrates a growing awareness that sovereignty enforcement requires a credible sea power.
Beyond the South China Sea, maritime tensions between ASEAN states themselves continue to shape procurement decisions. Thailand’s long-standing pursuit of submarines from China and Cambodia’s acquisition of advanced Chinese Type-056 frigates illustrate how overlapping claims over fisheries and potential maritime energy sources in the Gulf of Thailand fuel intra-regional capability upgrades.
In this environment, deterrence has returned as a key strategic concept for Southeast Asian navies. States increasingly believe that without a credible ability to impose costs, diplomatic claims risk being ignored, and national rights at sea may be eroded.
Non-Traditional Maritime Threats and Expanding Naval Missions
A second major driver of modernisation is the growing diversity of non-traditional maritime threats. Piracy, smuggling, illegal fishing, environmental and natural disasters further complicate naval responsibilities. Indonesia and the Philippines, two archipelagic states with thousands of islands, face this challenge acutely.
Indonesia’s 2025 floods in North Sumatra, which cut off isolated communities, revealed the importance of amphibious ships capable of delivering food, medical supplies, and rescue personnel. The damages caused by the flood in Indonesia were so extensive that the affected areas could only be reached through air and sea. Similarly, the Philippines, regularly battered by powerful typhoons, relies heavily on its Tarlac-class landing platform docks to transport relief goods and evacuate civilians as part of its humanitarian assistance operations. These humanitarian assistance and disaster response (HADR) operations have become defining missions for both countries.
Modern amphibious vessels, enhanced maritime lift, and flexible platforms are therefore not luxuries; they are necessities. As climate change intensifies, Southeast Asian navies will be expected to shoulder bigger responsibilities in national resilience and disaster management.
Economics, Energy, and the Maritime Lifelines of Southeast Asia
The third driver is economic and energy security. Southeast Asia’s prosperity relies heavily on secure maritime routes. The Malacca Strait, Sunda Strait, Lombok Strait, and South China Sea together form one of the world’s most important trading corridors. Disruptions to these sea lines of communication (SLOCs), whether due to piracy or geopolitical tension, carry direct national and regional economic costs.
The region’s maritime economy extends far beyond shipping lanes. Offshore oil and gas platforms, deep-sea minerals, fisheries, and coastal industries form crucial components of national GDPs. Territorial disputes over fishing zones and hydrocarbon blocks—in the Gulf of Thailand, Ambalat Sea, and throughout the South China Sea—underscore the high stakes involved. Piracy and sea robbery in the Strait of Malacca and Sulu-Celebes Sea remain persistent challenges, threatening commercial shipping and maritime workers. Thailand, for example, remains concerned about the vulnerability of its oil tankers travelling to and from Singapore.
ASEAN governments increasingly accept that economic security cannot be assured without secure maritime spaces. Protecting EEZs, deterring illegal extraction of resources, and ensuring safe navigation have thus become core naval missions.
Subsurface Modernisation: The Quiet Revolution beneath the Waves
One of the most striking trends in ASEAN naval development lies beneath the surface. Several Southeast Asian states are investing in submarines for deterrence, intelligence-gathering, and sea-denial missions.
Indonesia stands at the forefront. It has made notable technological gains with its locally produced unmanned underwater vehicles (KSOT), which have successfully conducted remote torpedo firings. For a country with vast maritime territory, such systems offer a cost-effective way to enhance sea-denial strategies.
Singapore is another ASEAN nation expanding its subsurface capabilities. The commissioning of the Invincible-class Type-218SG submarines in 2024 marked a major leap in regional underwater capabilities. These submarines, equipped with air-independent propulsion, are designed for extended, stealthy operations in congested littoral waters.
Several other ASEAN states are pursuing subsurface warfare capabilities. In 2025, Thailand signed deals for Chinese-built submarines after years of delays, while the Philippines is exploring the feasibility of establishing its first submarine fleet.
Surface Fleet Expansion: A Region Re-Arms at Sea
The region’s surface fleets are also undergoing substantial renewal. Singapore continues to pursue a systematic, long-term fleet transformation. Its eight Littoral Mission Vessels (LMVs) have replaced older patrol craft, while a new generation of Multi-Role Combat Vessels (MRCVs) and offshore patrol vessels is under construction. Even the advanced Formidable-class frigates are receiving mid-life upgrades to extend their effectiveness.
Indonesia’s modernisation is equally noteworthy. Jakarta has acquired or received used warships from Italy, South Korea, and Turkey, expanding its surface fleet. The Indonesian Navy is even considering the potential acquisition of a second-hand Italian aircraft carrier for HADR operations, reflecting an agenda focused not just on warfighting but on national resilience.
Manila’s procurement of Tarlac-class landing docks from Jakarta further illustrates growing regional defence-industrial cooperation. Malaysia meanwhile advances with its Gowind-derived Littoral Combat Ship programme and an ambition to field vessels optimised for anti-submarine, anti-ship and air-defence missions.
Conclusion: Toward a more Capable and Resilient Maritime ASEAN
ASEAN states’ naval modernisation wave is driven by converging strategic imperatives: contested waters, expanding non-traditional threats and the centrality of maritime resources to national prosperity. These pressures are reshaping Southeast Asia’s maritime landscape, compelling states to invest in more capable, flexible and resilient naval forces.
Whether this results in greater regional stability or exacerbates security dilemmas will depend on how governments balance deterrence with cooperation. Increased transparency between states, expanded naval hotlines and confidence-building measures will be critical. But the broader trajectory is clear: in an era of complex maritime challenges, ASEAN states are undergoing a strategic sea of change.
