Gulf of Thailand, April 7, 2025 – China and Cambodia launched a joint military exercise on April 6, 2025, at the newly expanded Ream Naval Base, a strategic facility on Cambodia’s southern coast facing the Gulf of Thailand. The drills, involving warships from both nations, included formation maneuvers and tactical simulations, according to China’s state broadcaster CCTV. The exercises commenced just one day after the formal inauguration of the upgraded base, which has drawn scrutiny from the United States and regional allies over fears it could bolster Beijing’s military footprint in Southeast Asia.
Background: Ream Naval Base Expansion
The Ream Naval Base, historically a modest Cambodian facility, underwent significant upgrades beginning in the early 2020s with Chinese financial and technical support. The expansion, completed in late 2024, added deep-water piers capable of accommodating aircraft carriers and submarines, advanced radar systems, and logistics infrastructure. While Cambodian officials insist the base is for national defense and humanitarian operations, U.S. intelligence reports and satellite imagery have long suggested the upgrades align with China’s broader ambitions to secure strategic outposts in the Indo-Pacific.
The U.S. and its allies view Ream as a potential node in China’s “string of pearls” strategy, which aims to establish naval footholds from the South China Sea to the Indian Ocean. The base’s location offers proximity to contested waters, including the Malacca Strait and the Spratly Islands, where China has built militarized artificial islands.
Joint Exercises and Regional Reactions
The April 6 drills featured at least four Chinese warships, including a Type 052D destroyer and a Jiangkai-class frigate, alongside Cambodian patrol vessels. CCTV described the exercises as “routine” and focused on “maritime security, disaster response, and interoperability.” Cambodian Defense Minister Tea Seiha emphasized the drills’ role in “strengthening bilateral trust” and dismissed external concerns as “unfounded speculation.”
However, the timing of the exercises—immediately following the base’s inauguration—signaled a deliberate display of Sino-Cambodian military alignment. The Straits Times reported on April 7 that U.S. officials had privately raised alarms about the base’s potential dual-use capabilities, which could allow China to station troops, aircraft, or missile systems in Cambodia.
“This isn’t just about a naval base. It’s about China embedding itself into Cambodia’s critical infrastructure,” said Derek Grossman, a senior defense analyst at the RAND Corporation. “Ream could serve as a forward operating site for Beijing to project power into the Gulf of Thailand and beyond.”
U.S. Concerns and Cambodian-Chinese Ties
U.S.-Cambodia relations have been strained since Phnom Penh canceled joint military exercises with Washington in 2017 and deepened ties with Beijing. China has invested over $10 billion in Cambodia through its Belt and Road Initiative (BRI), funding highways, ports, and the controversial Funan Techo Canal project. Critics argue these investments have eroded Cambodia’s autonomy, with Prime Minister Hun Manet’s government increasingly aligning with Beijing on geopolitical issues.
In 2023, the U.S. imposed sanctions on Cambodian officials over allegations of corruption linked to Ream’s construction. U.S. Secretary of State Antony Blinken reiterated concerns in 2024, warning that China’s militarization of the base “undermines regional stability and violates Cambodia’s constitutional neutrality.”
ASEAN’s Delicate Balancing Act
The Ream developments have also unsettled ASEAN members, particularly Vietnam and the Philippines, which have maritime disputes with China. Vietnam, which shares a maritime border with Cambodia, has quietly lobbied Phnom Penh to limit foreign military activities in the Gulf. Meanwhile, the Philippines—a U.S. treaty ally—recently bolstered its defense posture in the South China Sea amid repeated clashes with Chinese coast guard vessels.
ASEAN’s principle of non-interference has limited collective action, but diplomats acknowledge growing unease over Cambodia’s tilt toward China. “Ream sets a precedent,” said a Southeast Asian diplomat speaking anonymously. “It challenges ASEAN’s unity and complicates efforts to manage tensions in the South China Sea.”
China’s Strategic Calculus
For China, Cambodia represents a critical partner in its quest to counter U.S. influence in Asia. Access to Ream would complement its existing base in Djibouti and facilities in the South China Sea, enhancing its ability to patrol vital shipping lanes and respond to contingencies in the Taiwan Strait.
Chinese Foreign Ministry spokesperson Wang Wenbin defended the drills as “normal cooperation between sovereign states” and accused the U.S. of “hyping tensions to justify its military hegemony.”
Looking Ahead
The Ream Naval Base’s expansion and the recent drills underscore the deepening military dimension of China-Cambodia relations. While Phnom Penh maintains the base will not host foreign forces permanently, the lack of transparency fuels suspicions. As the U.S. recalibrates its Indo-Pacific strategy, Ream’s strategic value to China—and its implications for regional security—will remain a flashpoint.
For now, the Gulf of Thailand exercises serve as a symbolic assertion of Beijing’s growing reach, even as Southeast Asian nations grapple with the economic and geopolitical pressures of navigating U.S.-China rivalry.
