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