Beneath the Surface: The Second-Tier Supplier Vulnerabilities US Companies Are Only Now Beginning to Understand

For several years, the prevailing logic among American procurement executives has been straightforward: move production out of China, distribute across Southeast Asia, and declare the supply chain resilient. The strategy made intuitive sense. Vietnam, Indonesia, Thailand, and Malaysia collectively offer competitive labor costs, improving infrastructure, and governments eager to attract foreign capital. What many US firms failed to anticipate, however, was that diversification at the top tier of their supplier networks did not automatically translate into resilience deeper down the chain.

SuriaLink has spoken with supply chain consultants, regional trade analysts, and procurement officers at several mid-to-large US corporations over recent months. A consistent theme emerges: the deeper you look into Southeast Asian supply networks, the more concentrated—and therefore fragile—they become.

The Audit Gap

Most large US companies conduct rigorous due diligence on their Tier 1 suppliers—the factories and manufacturers with whom they have direct contractual relationships. It is the Tier 2 and Tier 3 layers where oversight tends to dissolve. These are the companies supplying raw materials, sub-components, and specialized inputs to the factories that US firms actually visit and audit.

In Southeast Asia, this gap is particularly pronounced. The region's rapid industrialization over the past decade has produced a dense ecosystem of smaller, often family-owned manufacturers and resource extractors who operate with limited transparency. Many lack the administrative infrastructure to respond to comprehensive supplier questionnaires, and few have undergone the kind of third-party environmental, social, and governance assessments that have become standard in more mature supplier relationships.

The result is a significant blind spot. A US electronics brand may have full visibility into its Vietnamese assembly partner's labor practices and quality controls, while remaining entirely unaware that the same partner sources a critical resin compound from a single small-scale chemical producer in a flood-prone industrial corridor outside Hanoi.

Indonesia's Nickel Concentration

Perhaps no single commodity illustrates the depth of this problem more clearly than nickel, a mineral central to battery manufacturing and therefore to the electric vehicle supply chains that dozens of American companies are now building out.

Indonesia holds an estimated 22 percent of the world's known nickel reserves and has aggressively positioned itself as the dominant global processor of the metal. For US manufacturers seeking to localize EV battery supply chains away from Chinese refiners, Indonesian nickel has appeared to be an attractive alternative. In practice, however, the processing infrastructure remains heavily concentrated among a small number of smelting operations, several of which have deep financial and operational ties to Chinese industrial groups.

For US companies subject to the Inflation Reduction Act's sourcing requirements—or those seeking to market their products as genuinely China-independent—this creates a significant compliance and reputational complication. The geographic origin of the ore may be Indonesian, but the refining pathway often runs through Chinese-affiliated entities before reaching American factories. Supply chain audits are only now beginning to surface this distinction, and the remediation options are limited given the current state of Indonesian refining capacity outside those relationships.

Vietnam's Semiconductor Assembly Bottleneck

Vietnam has emerged as a preferred destination for semiconductor packaging and testing operations, attracting substantial investment from US chipmakers and their contract manufacturing partners. The country's well-educated technical workforce, improving power infrastructure, and preferential trade terms have made it a credible alternative to Malaysia's Penang corridor for certain assembly operations.

What is less frequently discussed is the extent to which Vietnam's semiconductor ecosystem depends on a narrow base of domestic chemical and materials suppliers. Specialty gases, photoresists, and bonding materials used in chip packaging are, in many cases, sourced from a small cluster of Vietnamese and regional producers. Several of these suppliers operate single-facility production sites, creating concentration risks that a natural disaster, industrial accident, or regulatory action could rapidly translate into production stoppages across multiple US customers simultaneously.

The 2011 flooding in Thailand—which disrupted hard disk drive production globally for more than a year—remains the canonical example of what happens when a geographically concentrated supplier base encounters a shock it cannot absorb. Supply chain professionals who lived through that episode recognize the structural similarities in parts of Vietnam's current semiconductor materials ecosystem.

Thailand's Automotive Parts Web

Thailand has long been described as the Detroit of Southeast Asia, and with good reason. The country hosts a mature, deeply interconnected automotive manufacturing sector that supplies components to vehicle assemblers across the region and beyond. For US automakers and their Tier 1 suppliers who have established Thai operations, the ecosystem offers real advantages: skilled labor, established logistics networks, and decades of accumulated manufacturing expertise.

The complexity of that same ecosystem, however, creates its own category of risk. Thailand's automotive parts sector is characterized by long-standing relationships between assemblers and their upstream suppliers—relationships built on trust and proximity rather than formalized contractual structures. When US companies enter this network, either through acquisition, joint venture, or direct sourcing, they inherit dependencies that are not always visible in the documentation they receive.

A recurring finding in supply chain audits of Thai automotive suppliers is the presence of sole-source relationships for specific machined components or specialty alloys. A Thai Tier 1 supplier may have excellent quality metrics and strong financial health, while relying on a single family-owned foundry for a critical casting that has no qualified alternative source within a reasonable lead time.

What Forward-Thinking Companies Are Doing Differently

A growing number of US companies are responding to these realities by investing in more systematic supply chain mapping programs that extend beyond the Tier 1 level. These initiatives typically combine supplier questionnaire data with third-party intelligence tools that use trade flow data, satellite imagery, and local market research to identify concentration risks that self-reported data would not reveal.

Several firms have also begun building regional supply chain teams based in Southeast Asia—professionals with local language capability and on-the-ground networks who can conduct the kind of relationship-based due diligence that remote audits cannot replicate. This approach aligns with a broader trend toward treating Southeast Asian operations not as a procurement category managed from corporate headquarters, but as a strategic geography requiring dedicated expertise.

Finally, some companies are beginning to engage proactively with Southeast Asian governments on supplier development programs—working with industry ministries in Vietnam, Indonesia, and Thailand to support the qualification of alternative suppliers in critical categories. This longer-term approach requires patience and relationship investment, but it addresses the root cause of concentration risk rather than simply documenting it.

The Cost of Delayed Attention

The companies that are moving most deliberately on this issue are, almost uniformly, those that absorbed significant losses during the pandemic-era supply chain disruptions of 2020 and 2021. For firms that navigated that period with minimal impact, the urgency can be harder to sustain against competing budget priorities.

The risk of complacency is real. Southeast Asia's second-tier supplier ecosystem is growing rapidly, but it is doing so in ways that are not always legible to American procurement teams operating at a distance. The diversification strategies that US companies have pursued with considerable effort and capital over the past several years will only deliver their intended resilience benefits if the full depth of those supply chains is understood, mapped, and actively managed. The surface-level view, it turns out, was never the whole picture.