Reviewed by ThaiLawOnline, a licensed Thai law firm practising in Thailand since 2006. Thai lawyer of record: Wichuda Atthamethakon, LL.M., Thai Bar Licence 3149/2556.
Last updated on September 5, 2026
An inquiry official (พนักงานสอบสวน, phanakngan sopsuan, also translated as investigating officer or inquiry officer) is the police officer who, under the Thai Criminal Procedure Code, receives a criminal complaint, gathers evidence, questions the suspect and witnesses, and sends the inquiry file with an opinion to the public prosecutor. Section 120 of the Code bars the prosecutor from filing any case that has not first been the subject of an inquiry, so this officer controls the first and often decisive stage of every criminal case a foreigner meets, as suspect or as victim.
Table of Contents
Who the inquiry official is
The role is defined in Section 2(6) of the Criminal Procedure Code and assigned by Section 18 to police officers of the rank of sub-lieutenant and above in the district where the offence occurred or the suspect was arrested. The inquiry official records the complaint (คำร้องทุกข์) under Section 123, may summon and question witnesses, search with a warrant, seize evidence, take fingerprints and photographs, and arrest on a court warrant.
Section 134 requires the official, before questioning a suspect, to state the alleged facts and the charge and to warn that the statement may be used in evidence and that the suspect may remain silent. Sections 134/1 to 134/4 add the right to have a lawyer present, with one appointed by the state where the offence carries imprisonment and the suspect has none, and the right to a trusted person in the room. Section 13 requires an interpreter, who takes an oath, whenever the suspect does not understand Thai. Section 87 gives the police 48 hours to bring an arrested person before a court for remand.
Dealing with the inquiry official as a foreigner
As a victim, a foreigner should insist that the officer record a complaint that asks for prosecution, not merely an entry in the daily record book (บันทึกประจำวัน). The distinction matters for compoundable offences such as fraud and defamation, where the 3-month deadline runs from knowledge of the offence and only a proper complaint stops it. Bring the passport, documents and a Thai speaker.
As a suspect, the statement given to the inquiry official is the foundation of the file and is hard to retract at trial. The common mistake is to sign a Thai-language statement without a lawyer or a sworn interpreter, on the assurance that it is a formality. A suspect is entitled to read or have read back every page before signing, to refuse to sign, and to apply for bail from the same officer while the inquiry continues.
Inquiry official, public prosecutor and the court compared
| Stage | Who | Decides |
|---|---|---|
| Inquiry | Inquiry official at the police station | Whether to investigate, arrest, bail, and the opinion on the file |
| Prosecution | Public prosecutor, Sections 140 to 143 | Whether to indict, drop or order further inquiry |
| Trial | Court of First Instance | Guilt, sentence and bail during trial |
Under Sections 140 to 142 the official closes the inquiry with an opinion to prosecute or not and sends the file to the public prosecutor, who is not bound by it and may order further inquiry. The victim of a compoundable offence can bypass both by filing a private prosecution directly in court, but must then prove the case without the police file.
Frequently asked questions
What is an inquiry official in Thailand?
The police officer designated under Section 2(6) and Section 18 of the Criminal Procedure Code to receive complaints, investigate offences, question suspects and witnesses, and send the inquiry file with an opinion to the public prosecutor. No criminal case can be filed by the prosecutor without an inquiry under Section 120.
Do I have the right to a lawyer when questioned by Thai police?
Yes. Section 134/1 of the Criminal Procedure Code entitles a suspect to have a lawyer present during questioning by the inquiry official, and the state must provide one where the offence carries imprisonment and the suspect has none. Section 13 adds a sworn interpreter for a suspect who does not understand Thai, and the suspect may remain silent.
How long can Thai police hold a suspect before court?
Under Section 87 of the Criminal Procedure Code the inquiry official must bring an arrested person before a court within 48 hours, excluding travel time and days the court is closed. The court then decides on remand in blocks of up to 12 days, and bail can be applied for at the police station before that hearing or from the court after it.
See also: public prosecutor, bail, compoundable offence, criminal record, and the guides police interview in Thailand and the Criminal Procedure Code in Thailand.
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