Section 83 — Co-principals in an offence
English translation
In a case where any offence is committed by the act of two or more persons, those who take part in committing the offence together are principals and shall be liable to the punishment prescribed by law for that offence.
This English translation is provided for reference only and has not yet been firm-verified — always rely on the Thai original.
Firm annotation
Section 83, opening the Title on Principals and Supporters in Book 1, defines the co-principal. Its central idea is joint commission: where two or more people take part in committing the offence together, each is a principal and each bears the full penalty for the offence, regardless of the exact division of tasks between them. This makes it materially different from the accessory rules that follow: an instigator under section 84, a public advertiser under section 85, and above all a supporter under section 86, who is liable to only two thirds of the penalty. The dividing line is participation in the commission itself, as opposed to merely aiding it, and it is applied across the whole range of offences, from fraud to trespass to violent crime, by charging the substantive section together with section 83.
Why this matters in practice
Being fixed as a co-principal matters because it carries the full penalty, the same as if the person had committed the whole offence alone, so the fight is often over whether the accused truly took part in the commission or merely helped from the side. If the real role was only aiding or facilitating, argue for the supporter status under section 86 and its two-thirds cap instead. Co-principals can also be ordered jointly to return or pay for the property involved, so civil exposure often travels with the criminal finding. For businesses, joint liability shapes exposure across staff and directors; see corporate criminal liability in Thailand.
Supreme Court decisions interpreting this section
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Supreme Court Judgment No. 238/2568 (2025)
Two people who commit fraud together are co-principals under section 83 and each is liable to the full penalty for the offence.
Two defendants were convicted of fraud under section 341 read with section 83 as co-principals, each sentenced to two years and ordered to jointly return the money to the victim, illustrating full-penalty liability for joint commission.
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Supreme Court Judgment No. 3817/2568 (2025)
Persons who together intrude into and disturb another's possession of immovable property are co-principals in trespass under section 365 read with sections 362 and 83.
The court held that the defendants' joint conduct intruded into the plaintiff's possession of immovable property and disturbed its peaceful enjoyment, making them co-principals guilty of trespass under section 365 (2) read with sections 362 and 83.
Curated decisions with case numbers verified against the Supreme Court database. English renderings are the firm's editorial translation for study.
Frequently asked questions
Is a co-principal punished the same as a sole offender?
Yes. Under section 83, each person who takes part in committing an offence together is a principal and is liable to the full punishment prescribed for the offence, not a reduced portion.
How is a co-principal different from a supporter?
A co-principal under section 83 takes part in committing the offence and bears the full penalty, while a supporter under section 86 only aids or facilitates it and is liable to two thirds of the penalty.