Produced, not received

Bangkok is not Thailand’s richest province on the measure everybody quotes. Rayong is, and it is not close.

NESDC’s provincial product figures for 2022, published in its 2024 report:

And the other end:

Rayong is 1.6 times Bangkok and 16.5 times Narathiwat.

NESDC notes that the top-to-bottom ratio widened from 14.5 to 16.5 in a year, and describes the position as having deteriorated by 13.79%. At the regional level the highest-to-lowest ratio moved from 5.1 to 5.4.

So the headline is right: Rayong tops the table, and the spread is enormous and getting worse.

Now look at what the number counts.

GPP per capita is not income

It is Gross Provincial Product divided by registered population.

That is two decisions, and both of them do something to the answer.

The numerator is where things are made

Rayong’s figure is what it is because of Map Ta Phut — refining, petrochemicals, and the industrial estates of the Eastern Seaboard. Enormous value added, in a small province.

Value added is counted where the plant stands. It is not counted where the profit goes, and in a petrochemical complex the profit goes to shareholders — corporate groups headquartered in Bangkok, and international joint-venture partners headquartered a great deal further away.

A refinery in Rayong raises Rayong’s GPP. It does not put that money into Rayong households. Some of it arrives as wages, some as local procurement and some as tax. Most of the value added, by construction, is capital’s share, and capital does not live in Rayong.

This is not a Thai peculiarity. Every economy that measures production by location has the same property. It becomes a Thai problem when the resulting table is published under the heading “income per head” and read as a ranking of who is rich.

The denominator is where people are registered

And this is the part nobody says.

The population figure is registered population — ทะเบียนบ้าน. Where your name is on a household registration, not where you sleep.

Thailand’s industrial provinces are staffed substantially by people registered somewhere else. The Eastern Seaboard, Samut Sakhon, Samut Prakan and Ayutthaya all draw large workforces from the Northeast.

Which produces a specific and consequential effect. Consider one worker from Roi Et employed at a plant in Rayong.

Their output is in Rayong’s numerator. The value they add is counted in Rayong.

Their body is in Roi Et’s denominator. They are registered there, so Roi Et divides its own production by a population that includes someone producing nothing in Roi Et.

The same person makes Rayong’s figure higher and Roi Et’s figure lower, simultaneously.

Multiply that by the actual scale of internal migration and the 16.5× gap is doing something other than measuring how much better off a Rayong household is than a Roi Et household.

And the effect runs entirely in one direction. It is always the industrial province that gains and always the sending province that loses. The measure systematically flatters the destination and penalises the origin.

And a large part of the workforce is not counted at all

Article 40 The other foreigners covered Thailand’s migrant workforce from Myanmar, Cambodia and Laos.

They work in the numerator provinces — fishing, seafood processing, construction, manufacturing — and a great many of them are not in any Thai household registration.

Their output counts. They do not. Which raises per-capita figures in exactly the provinces that employ the most of them. Samut Sakhon sits seventh on this table.

The money that does move is invisible to the measure

Article 37 The pension system is called your children found the remittance economy: money travelling from the industrial provinces and Bangkok back to the Northeast, at a scale that functions as a private pension system.

Those flows are income received in Roi Et and produced in Rayong.

GPP per capita cannot see them in either direction. It does not deduct them from Rayong and does not credit them to Roi Et, because it is a production measure and remittances are a transfer.

Which means the single largest mechanism actually redistributing money between these provinces is absent from the table that is used to describe the gap between them.

What the number does and does not tell you

It tells you, accurately, where output is concentrated. That is genuinely useful. Rayong really does produce over a million baht of value added per registered resident, and Narathiwat really does not, and the industrial geography that produces that is real.

It does not tell you what a household in either province receives.

Those are different questions and Thailand has an instrument for the second one — the National Statistical Office’s household socio-economic survey, which asks households what they actually get.

I could not obtain a current provincial ranking from it, and I am not going to guess. The natural assumption is that Bangkok would top an income-received table rather than Rayong. That is an assumption. It is the obvious next thing to check and it would change the article’s ending.

The pattern, now named

This site has now found the same failure three times, and it is worth stating as a rule rather than as three coincidences.

Article 85 The tourists nobody counts found Thai domestic tourism undercounted, because the counting method was built around travellers who book accommodation. Article 148 The loudest junction found two published rankings of Bangkok’s worst junction sharing no entries, because one measured vehicle volume and the other measured complaints, and neither measured delay.

And here, a table headed with income that measures production location.

In each case: the quantity that matters is hard to observe, an easier proxy gets measured, and the proxy is then discussed as though it were the thing.

And in each case the proxy is not neutral. Tourism counting missed the poorest travellers. Junction complaints flattered the loudest districts. And GPP per capita flatters the province where the factory stands over the province where the worker’s family lives.

The gap between Thailand’s richest and poorest provinces is real, and it is widening on NESDC’s own account. The point of this article is narrower: the number we use to describe it is measuring where things are made, and the people it describes as poorest are partly the people who went and made them somewhere else.

---

Practically

If you are using this data, use it for what it is. GPP per capita is a good indicator of industrial concentration and a poor indicator of household prosperity.

If you are comparing provinces on how well people live, the household socio-economic survey is the instrument, along with poverty incidence, which NESDC also publishes.

And treat any single-year change in the ratio carefully. The top province’s figure is driven by refining margins and petrochemical prices, which move with global energy markets rather than with anything happening in Rayong. A year in which the ratio widens may be a year in which oil moved.

Common misconceptions

“Rayong is Thailand’s richest province.” Rayong has the highest output per registered resident. That is a different claim.

“Bangkok is the richest.” On this measure Bangkok is second. On household income received, nobody in this article has checked.

“The 16.5× gap shows how much poorer the Northeast is.” It shows a production gap, inflated by the fact that many Northeastern registrations belong to people working elsewhere.

“So the inequality isn’t real.” It is real, it is severe, and NESDC reports it widening. The measure overstates its size, not its existence.

“Per capita means per person living there.” It means per person registered there.