Thailand has introduced a comprehensive overhaul of its tax litigation procedures that will significantly impact how tax disputes are handled. The Regulations for Tax Cases B.E. 2568 (2025) take effect on November 24, 2025, and repeal the prior B.E. 2544 (2001) regulations in full. These regulations support the implementation of the Act on the Establishment of the Tax Court and Tax Case Procedure (No. 3) B.E. 2568 (2025), which expands the Tax Court’s jurisdiction to certain criminal tax matters. Published in the Government Gazette on October 14, 2025, the regulations have been reorganized into three parts covering civil cases, criminal cases, and forms, and are designed to accelerate proceedings, tighten evidentiary discipline, and modernize court operations.

Structural Reform and Scope

The prior regime governed only civil tax disputes. Under the new framework, the regulations introduce a dedicated chapter for criminal cases alongside updated civil procedures, as the Tax Court now has express authority to adjudicate specified criminal tax offenses. Select mechanisms applied in civil case proceedings, such as electronic communication, recording testimony, and appointing experts, also apply to criminal proceedings mutatis mutandis where they do not conflict with criminal procedure.

Civil Cases: Evidence Submission, Deadlines, and Scheduling

Parties must submit, together with the witness list, originals of all documentary evidence, media, or electronic data (such as files, USB drives, or CDs), and all physical evidence in the party’s possession. Failure to submit any original within the deadline (see below) results in a loss of the right to adduce that item at trial, subject only to narrow exceptions where submission is impossible due to force majeure or where receipt of the evidence is indispensable to the interests of justice. The practical impact is that parties are now obligated to assemble and verify all original documents and data at the very start of the case to meet the strict filing requirements.

The deadline to file witness lists and related evidentiary requests will now be at least 15 days before the hearing to determine the disputed issues—compared to the previous regulation, which set the deadline at 30 days before the hearing to determine the disputed issues.

The court also assumes a more active scheduling role. Upon accepting a complaint, the court must fix hearing dates and promptly notify the parties.

Criminal Cases: New Procedures and Interim Provincial Court Roles

The regulations’ new criminal chapter operationalizes the act’s expansion of Tax Court jurisdiction over criminal tax matters.

At the pretrial stage in provinces outside Bangkok, the provincial court acts on behalf of the Central Tax Court for investigative measures. These include issuing arrest and search warrants, granting or denying temporary release, ordering detention, and approving extensions of time to file charges.

Complaints may be filed with the provincial court where the offense occurred or is claimed or believed to have occurred, where the accused resides or was apprehended, or where the investigation was conducted. The provincial court must then notify the Central Tax Court, which assumes control of the case.

For cases filed by private plaintiffs, the provincial court will forward the original complaint to the Central Tax Court to schedule preliminary hearings.

For cases filed by public prosecutors, the provincial court will forward a copy of the complaint to the defendant and inquire whether the defendant has an attorney. The provincial court will then read and explain the complaint to the defendant and interrogate the defendant. Thereafter, the provincial court will forward the original complaint and the records of the defendant’s plea to the Central Tax Court for the decision on whether to conduct a preliminary hearing or accept the complaint.

For a case filed by a public prosecutor where the defendant pleads guilty and no witness examination is required for adjudication, coordination between the courts permits prompt adjudication. If a ruling is not made on the same day, the Central Tax Court may grant the defendant temporary release.

For trial proceedings, the Central Tax Court may select among three venues or modalities: hearings at the Central Tax Court in Bangkok, assignment of a Central Tax Court judge to preside at the local provincial court, and hearings conducted by videoconference, with the parties appearing at the provincial court under supervision and the proceeding being legally deemed to have occurred in the Central Tax Court’s courtroom. Witness testimony may likewise be taken remotely in accordance with the Criminal Procedure Code.

Provincial courts may manage preliminary steps, such as serving complaints and recording pleas, but do not adjudicate the merits.

For defendants in the provinces, this framework offers greater convenience for pretrial matters at the local court, while preserving centralized adjudication through flexible in-person, traveling-judge, or videoconference formats.

Parallel Civil and Criminal Tracks

In many tax disputes, both civil cases (such as appeals against tax assessments) and criminal cases (such as allegations of tax evasion) can arise from the same set of facts. The regulations maintain clear procedural separation of the cases in such a scenario. Parties facing both types of cases must plan and resource parallel litigation strategies, each with distinct timelines, filings, and evidentiary demands.

Practical Considerations

The regulations modernize Thailand’s tax litigation framework by accelerating case management, tightening evidentiary discipline, and extending the Tax Court’s reach to criminal matters with clear procedures and interim provincial court support.

Success under the new regime turns on preparation. Parties must ensure that all original documents, electronic media, and physical evidence are compiled, validated, and ready for submission well in advance of the 15-day witness list deadline. For criminal matters arising outside Bangkok, parties should anticipate local pretrial engagement at provincial courts and be prepared for trials to proceed either at the Central Tax Court, before a traveling tax judge, or via videoconference deemed to take place in the Central Tax Court’s courtroom.