Untangling Southeast Asia’s Maritime Security Complexities

Introduction

The Yellow Sea, separating China from the Korean Peninsula, has long been a theater of economic competition, strategic maneuvering, and diplomatic tension. It was here that the stage was set for two dramatic incidents that, when viewed side by side, reveal a telling contradiction in Northeast Asian geopolitics. North Korea, China’s historically, resorted to lethal violence against Chinese fishermen accused of illegal fishing. Meanwhile, South Korea, a close U.S. ally and frequent target of Chinese strategic pressure, responded to the erection of Chinese marine structures in contested waters with legal restraint choosing instead to pursue an amicable resolution through diplomatic channels. While this juxtaposition upends conventional expectations about alliances and rivalries, it also exposes the conflicting realities that underpin the region’s security landscape.

More often, China’s naval modernization and extensive claims in the South China Sea are identified as a significant maritime security concern in Southeast Asia. The Chinese government’s increasingly assertive approach to reinforcing its claims, from creating man-made islands equipped with military facilities to aggressive manoeuvres against Southeast Asian claimants, impacts regional maritime security.

As a result, the military modernization or expansion of Southeast Asian states, especially in the maritime domain, is argued to be primarily driven by the perceived threat from China. This may be true in some cases. For example, Malaysia plans to construct an additional submarine base in Sarawak on the island of Borneo to enhance the Royal Malaysian Navy’s ability to protect Malaysia’s Exclusive Economic Zone (EEZ) in the South China Sea, where Malaysia has overlapping maritime claims with China.

However, the China factor is not Southeast Asia’s only maritime security concern. Southeast Asian states’ maritime security challenges are shaped by a mix of economic interests, non-traditional security threats and intra-ASEAN overlapping maritime territorial claims.

Illegal Fishing

One major issue is the impact of Illegal, Unreported, and Unregulated (IUU) fishing on Southeast Asia’s fisheries industry, a significant economic sector in the region. More than 10 million people in the ten ASEAN states are employed in the fisheries sector, and in 2022, they contributed between 20% and 25% of global marine fish production.

Many Southeast Asian states have suffered economic loss from the threat of IUU fishing. It was estimated that in 2019, the ten ASEAN states incurred a loss of over $6 billion due to illegal, unreported, and unregulated (IUU) fishing.

The long-term sustainability of the fishing industry in Southeast Asia is questionable. Fish supply in regional waters is under threat, with an estimated 64% of the region’s fisheries at risk of collapse, primarily due to IUU fishing and China’s destruction of healthy coral reefs in the South China Sea to create artificial islands.

IUU fishing leads to dwindling fish stocks, reducing income and increasing poverty in Southeast Asia. Regional coastal communities are already feeling the impact of IUU fishing. In Cambodia, local fishermen have seen their catch and income fall due to IUU fishing, mainly conducted by Vietnamese trawlers. In the case of Malaysia, an estimated 980,000 metric tons of fish worth RM6 billion (or more than USD$1.3 billion) were stolen each year by illegal foreign vessels, mainly from Indonesia, Thailand and Vietnam.

Illegal Migration, Piracy and Terrorism 

Beyond IUU fishing, Southeast Asian states face a plethora of diverse maritime security challenges related to illegal migration, piracy and terrorism. These challenges pose an immediate domestic security concern for several Southeast Asian states.

Illegal migration in Southeast Asia is driven by conflict or economic factors. Violence against ethnic Rohingyas in Myanmar, worsened by the ongoing civil war after the 2021 coup by the Tatmadaw (Myanmar military), has led to an increasing outflow of Rohingya refugees by boats to Indonesia, Malaysia and Thailand. 

Malaysia is a magnet for Indonesians seeking better income, and many Indonesians entered Malaysia illegally, mainly using small boats. Out of an estimated 2.7 million Indonesian migrant workers in Malaysia, only about one-third are documented, reflecting the sheer number of Indonesians who most likely entered Malaysia illegally through the maritime domains. For Malaysia, its maritime enforcement agencies face clear and present dangers from Indonesian smugglers.

Piracy is another major security issue for Southeast Asia. Time Magazine mentioned Southeast Asian waters as the most dangerous waters in the world. Between 1995 and 2013, 41% of global pirate attacks occurred in Southeast Asia.

Thailand is a case in point that for some Southeast Asian states, their maritime security concerns are closer to home than the contested South China Sea. Bangkok’s maritime concern focuses more on the flow of Rohingya refugees from Myanmar and the security of its oil tankers travelling to and from Singapore, which are targeted by pirates operating small boats and supported by motherships manned by Indonesians.

For Singapore, piracy poses a significant challenge that could undermine its position as a maritime hub in Southeast Asia. Piracy in the Straits of Malacca and the Singapore Strait is of particular concern due to their proximity to the island state. Despite persistent efforts by Singapore to manage piracy in the Singapore Strait, attacks against vessels have increased by 35% between January and March 2025, compared with the same period the previous year. 

Terrorist acts in the maritime domain are another security concern. In the post-September 11  period, there have been unverified reports of political extremists boarding ships in Southeast Asia to conduct terrorist attacks at sea.

In 2005,  Lloyd’s Insurance declared the Malacca Straits and Singapore to be at risk from terrorist acts. It then raised insurance premiums and thus, business costs. Such threats persisted, and in 2010, Indonesia, Malaysia, and Singapore increased their sea and air patrols in the Straits of Malacca, following Singapore’s warning that attacks against shipping targets were being planned.

Several terrorist groups use the maritime domain to smuggle weapons or to aid one another. Jemaah Islamiyah members from Malaysia and Indonesia entered the Philippines for combat training through the Sulu Sea, which is surrounded by the three Southeast Asian states. The porous border in the Sulu Sea enabled weapons and drugs to be smuggled between Indonesia, Malaysia and the Philippines.

Intra-ASEAN maritime disputes

Besides China, Southeast Asian states have to contend with maritime territorial disputes with their immediate neighbors. These disputes are complex and deeply rooted in historical claims, resource competition, and strategic interests.

Cambodia and Thailand are contesting a maritime area of 27,000 square kilometers in the Gulf of Thailand, known as the Thailand–Cambodia Overlapping Claims Area (OCA). The OCA is believed to contain up to 11 trillion cubic feet of natural gas and 500 million barrels of oil.

The overlapping maritime claims with Thailand mainly drive Cambodia to expand its naval capabilities and operate larger, more modern Chinese Type-056 corvettes. The development of its Ream Naval Base, funded by China, aims to enable the Royal Cambodian Navy to monitor Cambodian waters better and address maritime threats from its immediate neighbors operating larger and more modern warships.

In March 2003, Bruneian and Malaysian naval vessels engaged in a standoff in the South China Sea over access to oil and natural gas resources within Brunei’s Exclusive Economic Zone (EEZ). Nevertheless, the dispute was resolved in 2009, with both parties agreeing to joint exploration.

In 2018-2019, maritime disputes between Singapore and Malaysia flared up when Malaysia unilaterally extended its port limits into Singapore’s territorial waters. As a result, government vessels and warships from both parties are facing off in the western part of the Singapore Strait.

Conclusion

External security partners such as Australia and South Korea must recognize that China, while a significant maritime security concern, is not the only factor that Southeast Asian states must confront. The latter faces a broad spectrum of challenges, including piracy, illegal fishing and territorial disputes among themselves. Focusing solely on China’s role risks overlooking these diverse security drivers and the region’s complex strategic environment. To engage effectively with Southeast Asian states and support regional stability, external partners must adopt a nuanced approach that addresses the full range of maritime concerns influencing the region’s evolving defense priorities.