Effective Number of Provinces in Each Thai Region by Revenue (2026)
In short
Central Thailand has 22 provinces but behaves like only 1.60 equal-sized ones by revenue, as of 17 July 2026. Bangkok alone books 78.4 percent of its regional revenue. The Northeast is the opposite case, with 20 provinces acting like 9.43. The East, with seven provinces, behaves like 3.00. Take Bangkok out of the Central region and the figure jumps to 5.49.
Which Thai regions behave like one-province economies?
Central Thailand does. It holds 22 provinces, yet its inverse-Herfindahl score is 1.60 (DBD, 2026). Its revenue is spread as if only one and a half equal provinces existed. Bangkok is the reason, with 78.4 percent of the region's 64.46 trillion baht. The East is the second tight cluster, at 3.00 effective provinces across seven. Chon Buri books 43.2 percent of East revenue. Rayong adds another 36.3 percent. The Northeast sits at the other pole, where 20 provinces behave like 9.43. Its biggest, Nakhon Ratchasima, holds just 22.7 percent. The score is simple: square each province's share of regional revenue, add the squares, and take the inverse. A region of ten identical provinces scores exactly ten.
Effective number of provinces by region
- Central2
- East3
- North4
- West4
- Central excluding Bangkok5
- South6
- Northeast9
Figures in effective provinces.
Central Thailand has the most provinces on paper and the fewest in practice. Compare each bar with the province count in the table below.
Region by region concentration
| Region | Provinces | Revenue in trillion baht | Effective provinces | Effective as share of provinces | Largest province | Largest province share |
|---|---|---|---|---|---|---|
| Central | 22 | 64 | 2 | 7.3% | Bangkok | 78.4% |
| East | 7 | 9 | 3 | 42.8% | Chon Buri | 43.2% |
| North | 9 | 1 | 4 | 40.3% | Chiang Mai | 43.8% |
| West | 5 | 1 | 4 | 74.8% | Ratchaburi | 42.7% |
| South | 14 | 2 | 6 | 45.1% | Songkhla | 28.1% |
| Northeast | 20 | 2 | 9 | 47.1% | Nakhon Ratchasima | 22.7% |
| Central excluding Bangkok | 21 | 14 | 5 | 26.1% | Samut Prakan | 34.6% |
Inverse-Herfindahl of province revenue within each of the six traditional regions, as of 17 Jul 2026. Revenue in trillion baht.
Why this matters
A region with many provinces can still be a one-engine economy. Central Thailand is the clearest case, and the 1.60 score says a shock to Bangkok is a shock to nearly the whole region. The East is a different story. It has few provinces but two heavy industrial anchors, so it behaves like three and not one. The West is the quiet outlier. It has only five provinces, yet it scores 3.74. That is 74.8 percent of its province count, the most even spread of any region relative to size. For anyone choosing where to open a branch or place a supplier, the Northeast and the South offer genuine choice. The North looks broad on a map but leans on Chiang Mai for 43.8 percent of its revenue. Strip Bangkok out and the rest of the Central region scores 5.49. The capital, not the region, is the concentration.
Definitions
- Herfindahl index
- The sum of squared shares. It rises as revenue piles into fewer places.
- Effective number of provinces
- One divided by the Herfindahl index. It is the count of equal-sized provinces that would give the same concentration.
- Region
- One of the six traditional groupings: North, Northeast, Central, West, East and South. Bangkok sits in Central.
- Revenue
- Total reported revenue of companies that filed a financial statement, booked to the province of registration.
Assumptions
- Revenue is booked to the registered province, so a firm headquartered in Bangkok with plants elsewhere counts in Bangkok. This inflates Central concentration.
- Only companies with a filed financial statement contribute revenue.
- Region boundaries follow the traditional six-region grouping. Other groupings would change the scores.
- Rows with no province, worth 24.4 billion baht, are excluded.
Methodology
Province revenue comes from the Department of Business Development registry aggregates, with rows computed on 17 July 2026. Each of the 77 provinces was assigned to one of six traditional regions: North 9, Northeast 20, Central 22 including Bangkok, West 5, East 7 and South 14. Within each region, each province's share of regional revenue was squared and summed to give a Herfindahl index, and the effective number of provinces is its inverse. Revenue is the total reported revenue of companies that filed a financial statement, booked to the registered province. Rows with no province, worth 24.4 billion baht, are excluded. The registry's own HHI column is empty and was not used.
How we verified this
- All 77 provinces were mapped to exactly one region, with counts 9 + 20 + 22 + 5 + 7 + 14 = 77.
- Bangkok share of Central revenue recomputed as 50.545 trillion divided by 64.461 trillion, which is 78.4 percent.
- Central inverse-Herfindahl recomputed from the 22 province shares at 1.60, and 1.60 divided by 22 gives 7.3 percent of headcount.
- West ratio recomputed as 3.74 divided by 5, which is 74.8 percent.
- Northeast ratio recomputed as 9.43 divided by 20, which is 47.1 percent.
- Province revenue summed across the 77 provinces is 80.06 trillion baht, and the national inverse-Herfindahl recomputed at 2.45, matching the sister page on national province concentration.
- Rayong share of East revenue recomputed as 3.200 trillion divided by 8.818 trillion, which is 36.3 percent.
- East effective share recomputed from the unrounded score 2.995 divided by 7, which is 42.8 percent, and Northeast, North, South, West and Central ex-Bangkok scores all recomputed from the 77 province revenue rows under the read-only role.
References
- Department of Business Development. (2026). Registered juristic persons and financial statement aggregates by province. Ministry of Commerce, Thailand. https://www.dbd.go.th/
Frequently asked questions
What is an effective number of provinces?
It is the inverse of the sum of squared revenue shares. It tells you how many equal-sized provinces would produce the same concentration. Central Thailand scores 1.60.
Which Thai region has the most even revenue spread?
The Northeast, with 9.43 effective provinces out of 20. The West is the most even relative to size, at 74.8 percent of its five provinces.
Is Central Thailand concentrated only because of Bangkok?
Largely yes. Without Bangkok the other 21 provinces score 5.49, with Samut Prakan the largest at 34.6 percent.
Why not use the registry's HHI column?
That column is empty in the registry aggregates, so the score was computed directly from province revenue.
Cite this page
Chatpong L. (2026). Effective Number of Provinces in Each Thai Region by Revenue (2026). Max Data Insights. https://maxdatathailand.com/insights/how-many-effective-provinces-does-each-thai-region-have-by-revenue-2026
Data & corrections
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Written by
Chatpong L.Founder, Max Data, Max Solutions Co., Ltd.
Chatpong L. leads Max Data, a company-intelligence platform built on Thailand's official business registry. He writes about the structure of the Thai economy using primary registry data. His work covers company formation, industry concentration, and regional business activity.
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This page reports company-level and aggregate statistics only. It names no individuals and makes no claims about any person. Figures are provided for information and may be revised as source data updates.