Article 128: Delegation of investigation duties
Statutory text (Thai original)
พนักงานสอบสวนมีอำนาจให้เจ้าพนักงานอื่นทำการแทน ดังต่อไปนี้
(๑) การใดในการสอบสวนอยู่นอกเขตอำนาจของตน มีอำนาจส่งประเด็นไปให้พนักงานสอบสวน ซึ่งมีอำนาจทำการนั้นจัดการได้
(๒) การใดเป็นสิ่งเล็กน้อยในการสอบสวน ซึ่งอยู่ในเขตอำนาจของตน ไม่ว่าทำเองหรือจัดการตามประเด็นมีอำนาจสั่งให้ผู้อยู่ใต้บังคับบัญชาทำแทนได้ แต่ทั้งนี้ เมื่อประมวลกฎหมายนี้หรือกฎหมายอื่นมิได้เจาะจงให้ทำด้วยตนเอง
English translation
An investigating officer has the power to have other officers act in his place, as follows: (1) for any matter in the investigation that is outside his jurisdiction, he has the power to send a commission to the investigating officer who has power over that matter to deal with it; (2) for any matter that is a minor part of the investigation within his jurisdiction, whether done by himself or dealt with under a commission, he has the power to order a subordinate to act in his place, provided that this Code or another law has not specifically required the matter to be done by himself.
This English translation is provided for reference only and has not yet been firm-verified. Always rely on the Thai original.
Firm annotation
This provision opens Chapter 1 (Ordinary Investigation) and provides practical flexibility so that an investigation is not paralysed by jurisdictional limits or workload. Sub-section (1) allows a commission (a request to an out-of-area investigator), while sub-section (2) permits delegation of minor tasks to subordinates. The key limit is that neither route can be used where the Code or another law requires an act to be done personally, such as the settlement of certain traffic offences. The courts read the boundary strictly: an officer who acts outside his jurisdiction without a proper commission is not treated as acting on delegation, and that investigation can be unlawful.
Why this matters in practice
For a defendant, this section is worth checking whenever the investigation crossed police-station boundaries or was handled by a junior officer. If an officer investigated outside his own jurisdiction without a proper commission under Section 128(1), that part of the investigation can be unlawful, which may affect the prosecutor's power to file. Some acts, like certain traffic-fine settlements, must be done by the investigating officer personally and cannot be delegated at all. If jurisdiction of the investigating station is in doubt, a review with a lawyer is worthwhile; see how to choose a Thai lawyer.
Décisions de la Cour suprême interprétant cette section
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Arrêt de la Cour suprême n° 2565/2565 (2022)
While some acts, such as settling a traffic offence, must be done personally by the investigating officer under Sections 38 and 144, Section 128(1) and (2) allow the investigator to request or order other officers to act in his place for certain matters.
The Supreme Court explained that a person who is not the investigating officer has no power to settle a traffic offence under the Land Traffic Act, since that is a personal power of the investigator under Sections 38 and 144. It noted, however, that Section 128(1) and (2) do allow the investigator to have other officers act in his place for certain matters, so the officer is not required to do everything personally.
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Arrêt de la Cour suprême n° 12934/2553 (2010)
An investigator who acts outside his jurisdiction, where none of the exceptions in Section 18 paragraph two applies, cannot be regarded as acting in place of the competent investigator under Section 128, and his investigation is unlawful; a later investigation by the competent officer may cure the defect.
An investigator from one station had no power to investigate because the offence occurred outside his jurisdiction and no exception under Section 18 paragraph two applied, nor could it count as acting in place of the competent investigator under Section 128, so his questioning was unlawful. However, once the file was sent to the competent station, that officer re-investigated the witnesses.
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Arrêt de la Cour suprême n° 371/2531 (1988)
Where an officer has no power to investigate because the offence occurred outside his jurisdiction and no exception under Section 18 paragraph two applies, his acts cannot be treated as acting in place of the competent investigator under Section 128, and the investigation is unlawful.
The Supreme Court held that a Bangkok-station officer had no power to investigate an offence that occurred in another district, and with no exception under Section 18 paragraph two, his questioning of the accuser's witness could not be treated as acting in place of the competent investigator under Section 128, so it was unlawful; the competent officer's later steps did not cure it because he had not treated his own part as complete.
Curated decisions with case numbers verified against the Supreme Court database. English renderings are the firm's editorial translation for study.
Cited in 5 Supreme Court decisions (1988 to 2022)
Décisions de citation sélectionnées
- Decision 12934/2553 (2010)
- Decision 2529/2549 (2006)
- Decision 3031/2547 (2004)
- Decision 371/2531 (1988)
- Décision 2565/2565 (2022)
Cette liste est sélectionnée automatiquement, en privilégiant les jugements qui reposent sur cet article plutôt que sur ceux qui se contentent de le citer lors du prononcé de la peine. Elle n'a pas encore été examinée par le cabinet.
Le plus souvent cité aux côtés de
- Article 120 3
- Section 2 3
- Article 18 3
Sections qui apparaissent le plus souvent dans les mêmes jugements que celui-ci. Le chiffre correspond au nombre de décisions.
Calculé sur l'ensemble du corpus de 83 652 décisions de la Cour suprême du cabinet, de 1921 à 2026. Le décompte est exhaustif ; la plage d'années indiquée élimine les valeurs aberrantes rares afin de refléter la répartition réelle des citations. Ces chiffres sont calculés par nos soins et ne constituent pas des statistiques officielles de la Cour. Comment nous les comptons et ce que nous avons mesuré
Foire aux questions
Un enquêteur peut-il déléguer certaines parties d'une enquête ?
Oui. En vertu de l'article 128, il peut envoyer une commission à un enquêteur extérieur à sa zone de compétence pour les affaires qui ne relèvent pas de sa juridiction, et peut ordonner à un subordonné de traiter des tâches mineures relevant de sa juridiction.
Existe-t-il des actes qui ne peuvent être délégués ?
Oui. Lorsque le Code ou une autre loi exige qu'un acte soit accompli personnellement, comme dans certains règlements d'infractions routières, l'agent enquêteur ne peut pas le déléguer.
Que se passe-t-il si un agent enquête en dehors de sa juridiction ?
S’il agit en dehors de sa juridiction sans mandat approprié en vertu de l’article 128(1), cela n’est pas considéré comme une délégation valable et cette enquête peut être illégale.
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Citer cette section
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Citation simple
Criminal Procedure Code, s. 128 (Thailand) -
Citation académique
Criminal Procedure Code (Thailand), s. 128. ThaiLawOnline, https://www.thailawonline.com/fr/thai-criminal-procedure-code/section-128/ (accessed 1 septembre 2026). -
Citation thaïlandaise
ป.วิ.อ. มาตรา 128 -
Lien permanent
https://www.thailawonline.com/fr/thai-criminal-procedure-code/section-128/ -
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<blockquote cite="https://www.thailawonline.com/fr/thai-criminal-procedure-code/section-128/"><p>An investigating officer has the power to have other officers act in his place, as follows: (1) for any matter in the investigation that is outside his jurisdiction, he has the power to send a commission to the investigating officer who has power over that…</p><footer>Criminal Procedure Code, s. 128 (Thailand): <a href="https://www.thailawonline.com/fr/thai-criminal-procedure-code/section-128/">ThaiLawOnline</a></footer></blockquote>
The Thai text is authoritative. The English is an unofficial translation by ThaiLawOnline, free to reuse with attribution.