Conduct is not risk

At December 2025 Thailand’s prisons held 301,020 people across 143 facilities designed for 248,330 — about 21% over capacity. The population had risen by roughly 20,000, or 7%, during the year, and around 70% of those held were in for drug offences.

That is the pressure behind everything else in this article. A system over capacity has to release people, continuously, and the question is not whether it releases them but how it chooses.

It chooses using a grade.

The six classes

Every sentenced prisoner in Thailand holds a classification — ชั้นนักโทษ — with six grades: ชั้นเยี่ยม (excellent), ชั้นดีมาก (very good), ชั้นดี (good), ชั้นกลาง (medium), ชั้นต้องปรับปรุง (needs improvement) and ชั้นต้องปรับปรุงมาก (needs much improvement). The framework sits under the Corrections Act B.E. 2560 (2017) and its ministerial regulations.

The class is the currency of the entire system.

Remission is calculated from it directly: ชั้นเยี่ยม earns five days off each month, ชั้นดีมาก four, ชั้นดี three. Eligibility for parole depends on it. Eligibility for external work programmes depends on it — article 126 The standard they set for themselves described one, where a day worked outside was a day off the sentence. And where periodic clemency instruments apply, the scale of benefit is graded by class as well.

Your class is, in a real sense, your release date.

So what does the class measure?

What a class is awarded for

Conduct inside the prison. Compliance with regulations, cooperation with staff, participation in work and training, absence of disciplinary incidents, orderliness over time.

Every one of those is a reasonable thing for a prison to want, and every one of them is measurable. A prison can observe them, record them, and review them on a schedule. As an administrative instrument the classification does exactly what it was built to do, and it does it consistently.

The difficulty is what it is being used for.

A class is a record of how somebody behaves in a controlled environment with no alcohol, no money, no relationships of the kind that produce most violence, no opportunity, and a staff member within shouting distance.

A release decision is a prediction about how somebody will behave in an environment with all of those things.

Those are not the same question, and the classification only answers the first one.

Which is article 119, in a building

That piece looked at why Thai drivers form confident theories about other drivers from the make of car, and found the answer was not prejudice. It was that in a system with almost no visible driver record, the vehicle was the only variable available. People reason from a bad signal when there is no good one.

A prison has the same problem with better paperwork.

Risk is not observable from inside a cell. What is observable is conduct, and conduct is recorded meticulously, so conduct becomes the number that decisions attach to. Not because anybody believes it is the same as risk. Because it is what there is.

And a calm, cooperative, punctual prisoner who committed a violent offence in circumstances that will exist again on the outside scores well on the only instrument the system runs. Nothing in the classification is designed to notice that, because the classification was not built to notice it.

That is the gap, and it is a design gap rather than a scandal.

What is missing has a name

An earlier version of this article said that a structured risk assessment is something the Thai system, on the published record, does not appear to run. That was wrong, and the correction makes the argument better rather than worse.

Thailand has one. In December 2023 the Department of Corrections set out five components of individual sentence administration, and the first of them is จำแนกลักษณะผู้ต้องขัง — classification by prisoner characteristics. On the department’s published description it studies history, background, personality and general condition in order to set custody plans and establish risk levels for supervision. Its basis is the Corrections Act B.E. 2560 (2017). The remaining components are the conduct grade, remission, parole, and one further instrument this article does not discuss.

So the system holds two classifications, and they measure different things. จำแนกลักษณะ asks who this person is and what supervision they need. ชั้นนักโทษ asks how they have behaved on the wing.

And the release arithmetic runs off the second one. Remission is five days a month at ชั้นเยี่ยม, four at ดีมาก, three at ดี — counted from the conduct grade, not from the risk classification. Parole and external work eligibility turn on the conduct grade too.

That is a sharper finding than the one I set out with. The problem is not that Thailand lacks a risk instrument. It is that it has one, and does not attach the release maths to it.

Risk instruments are imperfect and contested wherever they are used. They encode their own biases, they misclassify people, and there is a serious literature arguing they should be used carefully or not at all. But they are asking the question, and a conduct grade is not — and cannot be made to ask it by being calculated more carefully.

What I could not establish is how, or whether, the risk classification bears on release timing at all. The department publishes that it exists and what it is for. It does not publish a rule connecting it to the day somebody walks out, and that connection is the thing this article is about.

The number nobody agrees on

Reoffending is where this argument should be settled, and the Thai figures do not agree with each other.

There are three figures in circulation, and two of them can now be defined precisely.

The first two are the same measure and they are a stock. They answer what share of the people inside have been inside before — which is a fact about the composition of the prison population, not about what happens to anybody after they leave.

The third, if it means what it says, is a flow, answering what share of released people come back. Those are different questions with different denominators, and comparing them is the error the two numbers invite.

Which leaves two things worth saying rather than one.

On the same construction, the stock measure has risen from about a quarter to about two fifths. 23.74% in 2016 against 43% at the end of 2025 — and the later source reports that proportion as broadly stable across 2021 to 2025, so the change happened before that window. That is the number in this article I would most want an official series behind.

And the flow measure — the one that would actually evaluate release decisions — is not published in a form anybody can check. The Department of Corrections does track reoffending by release cohort, and its own data for releases between 2013 and 2023 shows most reoffending occurring within three years of release, then within two, then within one. The shape of the right measure exists. The rate does not, publicly.

That, in itself, is the finding underneath the finding. A country cannot evaluate whether its release decisions are working if the headline reoffending figure runs anywhere between a quarter and four fifths depending on who is speaking and what they are counting. The instrument is weak and the feedback loop that would reveal it is weaker.

The same July 2026 discussion put the economic cost of overcrowding and reoffending above ฿300 billion, which is the sort of number that gets a headline and which I would treat as an order-of-magnitude argument rather than an accounting figure.

Why the pressure makes it worse

A weak instrument under no pressure is a tolerable problem. A weak instrument carrying the weight of a system a fifth over capacity is a different thing.

When the buildings are full, the classification stops being one input among several and becomes the mechanism. It is the thing that can be applied at scale, consistently, to hundreds of thousands of files, without individual assessment. Its greatest administrative virtue — that it works mechanically — is exactly what makes it load-bearing when the system is under strain.

And overcrowding is not primarily a violence problem. Thai commentary is consistent that the population is heavily shaped by drug offences, which is a sentencing-policy question rather than a release-policy one. The people the classification struggles to assess are a small share of a very large number, and they are inside a machine built for the large number.

What would change it

Not longer sentences. This article is not making that argument and it should not be read as making it. A system that releases people badly is not improved by holding everybody longer; it is improved by choosing better.

A published risk instrument, separate from the disciplinary grade, applied to the offences where the question actually matters. That is a small number of cases relative to the population, and it is the number where the consequence of getting it wrong is highest.

And one reoffending series, defined once, published annually. Until that exists, nobody — including the department itself — can tell whether any change made anything better.

Common misconceptions

“Prisoners get out early because of leniency.” Release timing is calculated from an administrative classification with published rates: five days a month at the top grade, four and three below it.

“The class reflects how dangerous someone is.” It reflects conduct inside prison — compliance, work, absence of disciplinary incidents. It is not a risk assessment and was not designed as one.

“Thailand’s reoffending rate is known.” Reported figures range from about 24% to 80% depending on source and definition, and this article does not reconcile them.

“Overcrowding is caused by violent offenders.” Thai commentary consistently identifies drug offences as the dominant driver of the prison population.

“The answer is longer sentences.” This piece argues the instrument measures the wrong variable, not that the outcomes are too short.