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September 25, 2026

Thailand Seeks Comments on Proposed Merger Control and Market Dominance Rules

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On September 22, 2026, the Trade Competition Commission of Thailand (TCCT) opened a one-month public consultation period on proposed amendments to three key competition regulations, covering (1) the criteria for determining market dominance, (2) the definition of “monopoly” under Thailand’s premerger approval regime, and (3) the definition of a merger that may substantially lessen competition under Thailand’s postmerger notification regime. The public hearing period closes on October 21, 2026.

The proposed changes could significantly affect merger filing obligations and the assessment of market dominance under the Trade Competition Act B.E. 2560 (2017) (TCA).

The scope of the consultation and the proposed changes are outlined below.

Market Dominance Criteria

The draft notification on market dominance criteria proposes changes to the tests for both single-firm dominance and collective dominance, which would be measured using concentration ratios, as follows:

  • Single-firm dominance: The proposed changes would lower the market-share threshold from 50% to 33% and the sales-turnover threshold from THB 1 billion to THB 500 million for the preceding year.
  • Collective dominance: The three-firm concentration ratio (CR3) currently being used would be replaced by a two-firm concentration ratio (CR2). Under the new regime, the two largest operators in a relevant market would be considered dominant if their combined market share reached at least 75% in the preceding year. However, any business operator with sales turnover below THB 500 million or a market share below 10% would be excluded from this assessment.

In addition to static or numerical thresholds, the proposed notification introduces a dynamic threshold or alternative criteria for assessing dominance in markets that change rapidly, experience short-term fluctuations in demand or supply, or use technology as a platform for conducting business, such as digital markets.

Premerger and Postmerger Filing Thresholds

Under the TCA, a premerger filing is required if a merger transaction may result in a monopoly or market dominance, and a postmerger filing is required for any merger transactions that may cause a substantial lessening of competition. Apart from the proposed changes to the market dominance test discussed above, the draft notification on premerger filing thresholds revises the turnover threshold for monopoly status, which would be reduced from THB 1 billion to THB 500 million. Similarly, the draft notification on postmerger filing thresholds, which maintains a static numerical sales turnover threshold, reduces the threshold from THB 1 billion to THB 500 million.

Business Impact

The three proposals would establish THB 500 million as a common turnover threshold across several aspects of Thailand’s market dominance and merger control framework, replacing the current threshold of THB 1 billion. This would significantly broaden the scope of merger transactions subject to a filing obligation under the TCA.

The proposals also introduce a dynamic dominance assessment for rapidly changing and platform-based markets. This would make it more challenging for businesses undertaking a merger to assess their market share, competitive position, and merger filing obligations in the absence of a precise statutory threshold.

Beyond merger filing obligations, the reduction in the market share thresholds would also affect assessment of anticompetitive conduct, in particular abuse of market dominance. Smaller businesses could thus be deemed to hold a dominant position. While dominant status is not inherently illegal under the TCA, a dominant entity bears a special responsibility to ensure that its conduct does not restrict, distort, or foreclose competition. An entity seen to be abusing its market dominance could face criminal sanctions, including imprisonment for up to two years, a fine of up to 10% of income earned in the year in which the offense was committed, or both.

Next Steps for Business Operators

Participation in the consultation through local representatives or advisors is important for businesses that may undertake a merger transaction or may be affected by the revised criteria. The public hearing period provides an opportunity to explain how the proposed rules may operate in practice and to identify areas where further clarification may be needed.

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