OPINION | The Thailand Warning: What Pakistan's CHD620 Engine Problem Actually Teaches

by Ashu Mann

Thailand's troubled submarine program offers Pakistan a documented precedent on the risks of Chinese naval procurement, and the lesson it teaches is more sobering than most commentators have acknowledged.

In 2017, Thailand signed a government-to-government contract with China Shipbuilding and Offshore International Co. for one S26T Yuan-class submarine, with delivery expected in 2023. The vessel was specified with German MTU 396 marine diesel engines. In 2021, Germany halted engine exports, citing the EU arms embargo on China, a multilateral restriction in place since the 1989 Tiananmen crackdown, because the MTU 396 was classified as a military item. The embargo applies to all EU member states and any European-origin military engine manufacturer. China had no compliant European substitute and proposed its domestically produced CHD620 as the replacement.

What followed was four years of contested negotiations. Thailand threatened to cancel the submarine entirely and replace it with a Chinese-built frigate. In October 2023, the Thai government formally shelved the deal and directed the navy to proceed with a frigate instead. Then, in May 2024, Thailand reversed course entirely, agreeing to proceed with the submarine and the CHD620 engine. Thailand's cabinet formally amended the contract in August 2025, approving the engine substitution and extending the construction timeline by 1,217 days, roughly 3.3 years beyond the original delivery date. The compensation Thailand extracted after years of hard negotiation was real but modest: training simulators, insurance arrangements, crew training programs, and an agreement to purchase Thai agricultural exports as a partial offset.

After years of resistance, Bangkok ended up with the Chinese engine.

Thailand had meaningful leverage throughout this process. It formally canceled the deal, threatened a complete program switch, and had already paid 7.7 of 13.5 billion baht. It used that leverage across multiple years of public, documented negotiation conducted at the cabinet level and in the open. And it still accepted the CHD620. The warning Thailand issues is not that a determined buyer can hold out and win. It is that even a determined buyer with real leverage, a formal cancellation on record, and years of sustained public pressure ends up with the Chinese engine on extended timelines and limited compensation.

Pakistan faces the same supply-chain constraint without any of the leverage Thailand brought to bear. Its foreign exchange position is weaker, its debt burden heavier, and its relationship with Beijing more comprehensively dependent across CPEC, the JF-17 program, and wider bilateral financing. Pakistan accepted the CHD620 substitution without any publicly reported renegotiation. It extracted none of the warranties, compensation packages, or extended guarantees that Thailand spent years fighting for, or if it did, none of that was conducted in any forum visible to its parliament or its public.

The CHD620 itself warrants precise characterization. Thailand's navy chief, Admiral Adung Phan-iam, publicly disclosed in late 2023 that the CHD620 is a licensed Chinese-manufactured version of the MTU 396, the same German engine originally specified. A licensed copy and the original are not identical. Manufacturing tolerances, quality control standards, and long-term reliability in operational submarine conditions are distinct from licensing rights, and the CHD620's performance in combat submarine operations remains unvalidated by independent testing. Analysts assess its acoustic profile as inferior to the MTU it replaced, a significant liability in waters where India's anti-submarine detection infrastructure is expanding steadily.

Every major propulsion, electronics, weapons, and maintenance component on the Hangor class traces back to Chinese supply chains. Pakistan cannot service, certify, or upgrade these submarines without sustained Chinese cooperation. Thailand demonstrated that even a country with considerably more negotiating room, no broader strategic dependency on Beijing, and years of documented public resistance ultimately accepted the Chinese engine on Chinese terms. Pakistan accepted it without negotiating publicly at all.

The difference between those two outcomes is not the engine. It is institutional accountability. Thailand's entire process, the resistance, the cancellation, the reversal, and the final cabinet approval, is a matter of public record. Pakistan's acceptance was silent. The submarines are in the water, and the terms on which they were acquired remain unknown to the public paying for them.

---

About the Author

Ashu Mann is an Associate Fellow at the Centre for Land Warfare Studies. He was awarded the Vice Chief of the Army Staff Commendation card on Army Day 2025. He is pursuing a PhD from Amity University, Noida, in Defence and Strategic Studies. His research focuses include the India-China territorial dispute, great power rivalry, and Chinese foreign policy.

Disclaimer: This article represents the author’s independent analysis and perspective based on publicly available information. It does not constitute official guidance, intelligence assessment, or policy recommendation, and does not reflect the positions of Access Hub or any affiliated entities.