Sustainability reporting across Southeast Asia is undergoing a quiet but consequential transformation. What was once a fragmented landscape of country specific ESG frameworks is now moving toward a shared baseline aligned with standards set by the International Sustainability Standards Board. As this shift accelerates between 2025 and 2026, investors are finding it easier to compare companies across borders, and harder for weak governance or poor climate risk management to remain hidden. Across ASEAN, regulators in markets such as Malaysia, Vietnam, Thailand, and the Philippines are revising disclosure requirements to converge with ISSB standards. The result is not just regulatory harmonisation, but a more disciplined investment environment where sustainability information is increasingly tied to enterprise value, risk management, and long term capital allocation.

From Fragmented ESG Rules to a Regional Baseline

For years, sustainability reporting in ASEAN reflected national priorities rather than regional comparability. Some markets adopted mandatory ESG disclosure early, while others relied on voluntary guidance. That divergence made cross border analysis difficult and allowed companies to frame sustainability narratives in ways that were hard to verify. ISSB alignment is changing that dynamic. Established in 2021, the ISSB was created to consolidate disparate ESG reporting approaches into a single global baseline designed for investors. Its first two standards, IFRS S1 and IFRS S2, came into effect for reporting periods starting in 2024, but adoption depends on whether national regulators formally implement them. Across ASEAN, that process is now well underway. The convergence is also being shaped by external pressure, particularly from the European Union, where sustainability and climate rules increasingly affect exporters and multinational supply chains. For many Southeast Asian regulators, ISSB alignment is seen as a way to reduce compliance complexity while maintaining access to global capital and trade.

How ASEAN Markets Are Moving at Different Speeds?

While the destination is becoming clearer, ASEAN countries are arriving there from very different starting points. Malaysia has required listed companies to publish sustainability information since 2016 and expanded mandatory reporting in 2024 to large non listed companies with annual revenue above USD 225 million. Vietnam introduced mandatory sustainability disclosures in 2021 and is now revising its framework to align more closely with ISSB requirements. Singapore mandated climate related reporting from 2025, including Scope 1 and 2 emissions, although regulators have since announced a five year implementation delay. Thailand began mandatory climate reporting in 2022. Indonesia required banks to disclose sustainability information in 2019 and extended the requirement to listed companies in 2020. The Philippines is preparing to introduce mandatory ISSB aligned sustainability reporting from 2026. Along with Cambodia, Myanmar, Laos, and Timor Leste, it remains among the few ASEAN economies without comprehensive mandatory sustainability reporting today. As global measures such as the EU’s Carbon Border Adjustment Mechanism begin to influence trade competitiveness, these gaps risk raising compliance costs and limiting market access for companies that fall behind.

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What IFRS S1 and S2 Change for Investors?

ISSB’s two core standards are designed to integrate sustainability disclosures more closely with financial reporting. IFRS S1 establishes the overarching framework for reporting sustainability related risks and opportunities that affect strategy, cash flows, and enterprise value. It applies an investor focused materiality lens and requires sustainability information to be reported on the same basis, timeframe, and currency as financial statements. IFRS S2 focuses specifically on climate. Drawing heavily from the TCFD framework, it requires companies to disclose exposure to physical risks such as flooding or heat stress, transition risks linked to decarbonisation policies or carbon pricing, and climate related opportunities. It also mandates scenario analysis and explanations of how climate considerations are embedded in long term planning and resilience strategies. For investors, this moves sustainability reporting away from narrative positioning and closer to decision useful data that can be assessed alongside traditional financial metrics.

Comparability Raises the Bar for Corporate Credibility

Carlo Chen Delantar, Partner and Head of ESG at venture capital firm Gobi Partners, sees ISSB alignment as a structural improvement for the region’s investment ecosystem. As more countries converge on the same standards, he argues, investors can finally compare companies across ASEAN on a like for like basis. He notes that narrative driven sustainability reporting often allowed companies to emphasise what they wanted investors to see. Quantified disclosures anchored in enterprise value shift the focus. Instead of asking which company tells the most compelling story, investors are now asking who has credible data, realistic assumptions, and management teams that understand how sustainability affects cash flows and the cost of capital. Once comparability becomes the norm, weak disclosures no longer blend into the background. Gaps in governance quality or climate risk management stand out more clearly, and those gaps are increasingly penalised by investors, customers, regulators, and lenders.

Disclosure Quality as a Proxy for Management Strength

As ISSB aligned reporting becomes more widespread, disclosure quality itself is emerging as a screening tool. Investors are paying closer attention to whether sustainability data is auditable, consistent, and timely. Companies that meet these standards tend to exhibit stronger internal controls, clearer accountability, and faster decision making. According to Chen Delantar, high quality disclosure often reflects deeper organisational capability. It signals that management understands how sustainability risks translate into operational and financial outcomes. In this sense, reporting is no longer just about compliance. It becomes a window into how a company is run.

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Capital Access and the Cost of Weak Data

The implications extend beyond investor perception. A recent report by the Association of Chartered Certified Accountants highlights that access to capital is increasingly linked to the robustness of sustainability plans and demonstrable progress against targets. For companies seeking cross border financing or international investors, weak or inconsistent disclosures can translate directly into higher financing costs or reduced interest. The ACCA report also points to persistent challenges across ASEAN. Data quality remains uneven, and many companies lack internal systems or expertise to meet rising disclosure expectations. In a region where foreign direct investment plays a critical role and capital flows from the US, EU, and Japan are significant, these weaknesses can erode competitiveness.

Sustainability Reporting as Organisational Capability

Rather than viewing ISSB aligned reporting as a one off compliance exercise, Chen Delantar describes it as a capability that develops over time. He likens it to building a muscle. Many companies did not need to exercise it in the past, but once they begin, it changes how decisions are made and how risks are evaluated. As sustainability disclosures become embedded in financial language, they influence strategy, governance, and capital allocation. Companies that invest early in systems, data, and skills are likely to adapt more easily as standards evolve.

A New Definition of Investability in ASEAN

As ASEAN moves toward shared sustainability standards, the dividing line between companies is shifting. The question is no longer whether a company reports on ESG issues, but whether it is structurally capable of producing credible, decision useful disclosures. Chen Delantar compares companies to seeds growing into trees. Those rooted in strong foundations of governance, risk management, and data integrity are better positioned to withstand regulatory change and market scrutiny. In an increasingly aligned regional landscape, it is that foundation, rather than the timing of regulation, that will determine which companies attract capital and which struggle to remain investable.

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