Section 31 — Prosecutor joining the injured person
Statutory text (Thai original)
คดีอาญาที่มิใช่ความผิดส่วนตัวซึ่งผู้เสียหายยื่นฟ้องแล้ว พนักงานอัยการจะยื่นคำร้องขอเข้าร่วมเป็นโจทก์ในระยะใดก่อนคดีเสร็จเด็ดขาดก็ได้
English translation
In a criminal case that is not a compoundable offence which the injured person has filed, the public prosecutor may submit a motion to join as a co-plaintiff at any stage before the case becomes finally settled.
This English translation is provided for reference only and has not yet been firm-verified — always rely on the Thai original.
Firm annotation
Section 31 completes the pair started by Section 30 by letting the public prosecutor join a case the injured person has already filed, provided the offence is not a compoundable (private) one. The prosecutor's window is wider than the injured person's under Section 30: the motion may be filed at any stage before the case becomes finally settled, not just before the first-instance judgment. Together, Sections 30 and 31 are the only two routes to becoming a co-plaintiff in a criminal case; outside these situations, a stranger to the case cannot join.
Why this matters in practice
For an injured person prosecuting a serious, non-compoundable offence, the prosecutor stepping in can add investigative weight and resources to your case. Note the limit: this route is closed for compoundable offences, where the case stays purely private. If you have filed a private prosecution and want the state to join, or you are unsure whether your offence is compoundable, speak with a Thai lawyer.
Supreme Court decisions interpreting this section
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Supreme Court Judgment No. 3797/2540 (1997)
Sections 30 and 31 are the only routes to co-plaintiff status, covering the injured person joining the prosecutor or the prosecutor joining the injured person in a non-compoundable case; no one outside these two situations may join as co-plaintiff.
An applicant who was neither the injured person nor the prosecutor sought to join a case the prosecutor had filed. The court held that joining as co-plaintiff exists only in the two situations set out in Sections 30 and 31; outside them no joinder is possible, so a person who is not the injured party cannot join the prosecutor.
Curated decisions with case numbers verified against the Supreme Court database. English renderings are the firm's editorial translation for study.
Frequently asked questions
Can the public prosecutor join a case the victim already filed?
Yes, if the offence is not compoundable. Under Section 31 the prosecutor may join as co-plaintiff at any stage before the case becomes finally settled.
What is the difference between Section 30 and Section 31?
Section 30 lets the injured person join the prosecutor before the first-instance judgment. Section 31 lets the prosecutor join the injured person's non-compoundable case, with a longer window running until the case is final.
Can a third party who is not the victim join as co-plaintiff?
No. Sections 30 and 31 are the only ways to become a co-plaintiff, and both require being the injured person or the prosecutor. A stranger to the case cannot join.