--- title: "sSET Index: Methodology" description: "sSET Index is maintained by Stock Exchange of Thailand and covers Thai small-cap equity benchmark. How the index selects and weights its constituents." canonical: https://www.getswoopr.com/stocks/indexes/sset/ source: "Swoopr Investment: https://www.getswoopr.com" --- # sSET Index: What It Measures and How It Is Built ## Direct Answer > The sSET Index is a rule-based measurement of Thai small-cap equity benchmark, maintained by Stock Exchange of Thailand. Like every index it owns nothing: it is a number produced by applying a published weighting formula to a selected list of companies, revised on a schedule the provider sets. ## What this index covers The sSET Index covers Thai small-cap equity benchmark, within the Thailand market. Stock Exchange of Thailand defines which securities are eligible, how they are selected from that pool, and how much each one contributes to the published number. The index name does not state a fixed company count, so the number of constituents follows the eligibility rules rather than a target. ## How constituents are weighted Market capitalization weighted, with no weight cap or free float factor stated for this index. The weighting method is the single biggest driver of how an index behaves. Two indexes covering the same market can diverge for years purely because they weight differently, which is why comparing index levels without knowing the method tells you very little. ## What qualifies for inclusion Securities that are not in the SET100 Index in the same review and whose cumulative market capitalization falls between 90% and 98% of the total for all common stocks on SET. Each needs monthly volume of at least 0.5% of registered shares in 3 of 4 trading months and no market surveillance measure. Eligibility rules are the part of an index most readers never look at and the part that decides what it can possibly measure. A screen that excludes a whole sector, or admits only one listing venue, shapes the result far more than any day of trading does. ## How long a listing must exist first Basic qualifications for the tradable group apply: listed for no less than 6 months, no long suspension, no bankruptcy or debt default, and no disclaimer or adverse audit opinion. At least 20 percent free float is also needed. A seasoning rule is why a large new listing does not appear in an index the week it starts trading. It is a deliberate lag, and it means an index can under-represent a fast-growing part of the market for months at a time. ## When the membership is revised Reviewed twice a year, with changes effective in January using data to the end of November and in July using data to the end of May. Reconstitution is the one date an index changes shape by design rather than by price. Funds tracking it have to trade toward the new membership, which is why the schedule matters to anyone holding the tracker rather than only to the provider. ## The rule that surprises people The index is defined by a band of cumulative market capitalization outside the SET100, and every security that qualifies is included, so the number of constituents is not fixed. ## References - [Stock Exchange of Thailand: Stock Exchange of Thailand Ground Rules for SET Index Series](https://media.set.or.th/set/Documents/2025/Feb/Index_Ground_Rule_EN.pdf), as published 2026. Every rule described on this page is taken from this document. ## Current sSET Index constituents Stock Exchange of Thailand publishes and licenses the sSET Index constituent list. Swoopr does not republish it here. The provider's own page is the authoritative source for current membership and weights. [Stock Exchange of Thailand: official sSET Index page](https://www.set.or.th/en/market/index/setindex) ## Related reading - [All stock market indexes](https://www.getswoopr.com/stocks/indexes/): how indexes are built, weighted and revised. - [Emerging Markets indexes](https://www.getswoopr.com/stocks/indexes/emerging-markets/): others covering the same region. - [Index concentration](https://www.getswoopr.com/technical-analysis/market-concentration/index-concentration/): measuring how much of an index sits in its largest holdings. - [Index rebalancing and inclusion effects](https://www.getswoopr.com/stocks/corporate-actions-catalysts/index-rebalancing-and-inclusion-effects/): what happens to a stock when index membership changes. ## Frequently Asked Questions ### Who maintains the sSET Index? Stock Exchange of Thailand maintains the sSET Index and publishes the methodology document that defines its eligibility and weighting rules. ### What does the sSET Index measure? It measures Thai small-cap equity benchmark. The index is a calculated number applying a weighting formula to a selected list of companies, and it holds nothing itself. ### Where can I see the current sSET Index constituents? Stock Exchange of Thailand publishes the current constituent list. Swoopr does not republish it, because index providers license constituent data and Swoopr holds no such licence. ## About the author The [Swoopr Editorial Team](https://www.getswoopr.com/authors/swoopr-editorial-team/) writes Swoopr Investment's educational library, covering market structure, analysis methods and the mechanics behind the numbers investors read every day. Our [editorial policy](https://www.getswoopr.com/legal/editorial-policy/) and [corrections policy](https://www.getswoopr.com/legal/corrections-policy/) set out how this content is produced, reviewed and fixed when it is wrong.