The "Double Majority" rule, established under Section 13 of the Referendum Act B.E. 2564, imposes a dual-layer requirement for referendums to be valid. First, more than half of all eligible voters must participate. Second, among those who vote, more than half must approve the proposal. For example, with 40 million eligible voters, at least 20 million must cast ballots (first layer), and at least 10 million of these must vote in favor (second layer).

This rule is often applied to constitutional amendments in Thailand, ensuring public participation in such decisions. However, its strict conditions make it more difficult for referendums to pass. Critics argue that opponents of a proposal could boycott the referendum to reduce voter turnout below the required threshold, effectively invalidating the process.

As a result, the Double Majority rule has become a contentious issue in Thai politics, with concerns that it could hinder constitutional reforms by setting overly rigid requirements for public approval.