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Cambodia's Senate President Hun Sen and Paetongtarn Shinawatra, Thailand's prime minister (Tang Chhin Sothy and Valeria Mongellivia Getty Images)

Personality over protocol: Thailand-Cambodia tensions reveal ASEAN’s quiet crisis

Hun Sen’s leaked recording of Thai PM exposes how unregulated informal diplomacy can threaten regional stability.

Vu Lam

26 June 20255 min read

On 15 June, Thai Prime Minister Paetongtarn Shinawatra made a private phone call to Cambodia’s Senate President Hun Sen, a former prime minister who remains the dominant political figure in the country. The call was meant to de-escalate tensions following a deadly border clash that had reignited long-standing disputes near the Preah Vihear temple. It was conducted informally, personally, and outside official diplomatic channels.

Three days later, a nine-minute audio excerpt was leaked.

Hun Sen admitted to recording and disseminating the call, later releasing the full 17-minute audio on Facebook. What followed has been political chaos in Thailand: a coalition partner withdrew from government, protests erupted, and the Thai Foreign Ministry lodged a formal protest with Cambodia, and Paetongtarn now faces a no-confidence vote in parliament.

The fallout was not just a bilateral misstep; it exposed a structural vulnerability in how diplomacy is increasingly conducted. This incident serves as a textbook case of protocol vulnerability: the risks that arise when state-level diplomacy proceeds through undocumented, unaccountable, and unprotected means. More broadly, it illustrates what may be termed diplomatic authority drift, the growing trend of foreign policy influence shifting to individuals outside formal executive roles, often without mandate or oversight.

ASEAN member states have long relied on personal rapport and backchannels to manage tensions, but the Thailand–Cambodia incident highlights the risks of informality when it lacks procedural anchors.

At the heart of the Thailand–Cambodia case lies a misalignment of status and authority. Paetongtarn is the sitting head of government. Hun Sen, while no longer prime minister, retains unparalleled political sway. His son, Hun Manet, is the formal counterpart – yet it was Hun Sen who took the call, recorded it, and made it public.

This is a form of hybrid leadership diplomacy, where former leaders operate without clear accountability yet retain access to the levers of statecraft. For Paetongtarn, engaging directly with Hun Sen may have felt natural, rooted in familial ties and political history. But in bypassing formal channels, she exposed herself to reputational and political risk. Unlike official bilateral meetings, private engagements offer no diplomatic immunity, no archival record, and no crisis management structure.

Once public, they become political weapons.

ASEAN member states have long relied on personal rapport and informal backchannels to manage tensions as part of “the ASEAN way”. But the Thailand–Cambodia incident highlights the risks of informality when it lacks procedural anchors. The region has no shared norms or safeguards to govern the use of such channels, leaving bilateral diplomacy vulnerable to personal discretion and political exploitation. The risks do not stem from personal rapport itself – which remains a valid and often effective diplomatic tool – but from informality without norms. Private calls bypass institutional records, oversight mechanisms, and contingency planning.

An audience member holds a phone to photograph a speaker at an ASEAN podium (ASEAN Secretariat/Kusuma Pandu Wijaya)

Formal settings have an expectation of sorts (Kusuma Pandu Wijaya/ASEAN Secretariat)

This is not unique to Southeast Asia. During the first Trump administration, high-level engagement by non-official actors such as Jared Kushner and Rudy Giuliani frequently bypassed formal channels, blurring lines of authority. As the State Department’s role has diminished, the US itself has become susceptible to diplomatic authority drift. This is a reminder that even in well-established systems, diplomatic norms can erode when political leaders personalise foreign policy without effective institutional checks.

In Southeast Asia, however, this drift is compounded by institutional silence. ASEAN’s broader architecture, such as the ASEAN Charter and practices such as the rotating Chair or the Secretary-General’s mandate, offers no formal or informal norms to manage such hybrid situations. Bilateral relations have, quite naturally, been treated as sovereign matters.

But for a grouping that aspires to regional centrality and quiet diplomacy, the absence of shared expectations around diplomatic conduct is increasingly untenable. ASEAN’s non-interference principle, while crucial for its founding and stability, paradoxically means it generally avoids directly addressing the legitimacy of individual political actors or intervening in what are seen as “bilateral” incidents. Yet its silence leaves its diplomacy exposed to personalist improvisation with regional consequences.

The recent episode is emblematic of a wider pattern. In Malaysia, Mahathir Mohamad’s second premiership was marked by personal engagements that often bypassed formal coordination. In Myanmar, the NLD government maintained a hybrid model of civilian diplomacy and military backchannels prior to the 2021 coup. Elsewhere, dynastic or elder figures continue to exercise strategic influence without formal roles. In each case, personalism fills an institutional void – but also risks misalignment.

This is not the first time ASEAN’s diplomatic architecture has shown its limits. In earlier commentary on the Myanmar crisis, I warned of a “parallel diplomacy trap”, where some informal, ad hoc engagement efforts supplant the formal structures ASEAN relies on to maintain coherence. The Paetongtarn–Hun Sen call is a vivid example of this dysfunction playing out bilaterally. Good-faith outreach, when unanchored, can trigger crisis. The outcome is not flexibility, but friction.

ASEAN’s model of informality is not the problem; its lack of complementary norms is. What is needed is not heavy-handed institutionalisation, but a set of shared understandings – soft norms that clarify the difference between personal engagement and official diplomacy.

Three practical steps could begin this process. First, ASEAN should encourage member states to document high-level informal engagements within existing diplomatic protocols. Second, it could promote shared understandings around the use of non-executive actors in foreign policy dialogue. Third, it could discreetly empower the ASEAN Chair or Troika to advise or caution members when diplomatic practice threatens regional stability.

These proposed norms are not a call for ASEAN to abandon non-interference or to mediate bilateral disputes. Rather, they are about building a shared understanding of diplomatic conduct – one that helps contain the collateral damage when informally managed bilateral issues unexpectedly destabilise broader relations. This should not be confused with Track II diplomacy or the role of public diplomacy actors, which deliberately operate outside state authority. The concern here is different: when individuals embedded in the state apparatus, but without formal mandate, perform foreign policy functions without oversight.

The Thailand–Cambodia call leak revealed how easily personalised diplomacy can spiral into political crisis. For ASEAN, the challenge is not to abandon its informal culture, but to protect it – by ensuring it is not left to the whims of legacy actors or private calculations. Without that, ASEAN will remain a diplomatic community that celebrates consensus yet lacks the tools to protect the very process on which consensus depends.

The views expressed in this article are the author’s own and do not reflect those of his workplace and affiliated institutions.

About the author

Vu Lam

Dr.

Topics

ASEAN Cambodia Thailand Diplomacy