A similar concept to legal professional privilege or attorney-client privilege exists in the Thai legal system. It can be found in various legislative instruments, and in particular, those concerning court proceedings or litigation in the Thai courts. Additionally, it is a criminal offense for lawyers to divulge confidential information concerning attorney-client communications without the client's consent. The four main relevant legislative instruments are the following:

Penal Code

The Penal Code imposes an obligation on licensed lawyers, legal advocates, and other professionals (e.g., doctors and nurses) not to disclose any confidential information they know or receive as a result of carrying on their profession if such disclosure could or would result in damage to another person. The Penal Code protects not only the client but also other persons who would be injured by such disclosure.

Lawyer Act and the regulations on professional ethics of lawyers

The relevant provision in relation to attorney-client privilege provides that a licensed lawyer must not disclose or divulge any confidential information of the client that they obtain in their capacity as a lawyer unless consent from the client is obtained. The provision only applies to a lawyer who is licensed under the Lawyer Act.

Civil Procedure Code

The Civil Procedure Code provides that a licensed lawyer is entitled to refuse to give testimony or provide evidence that they are entrusted with or receive from the client unless consent from the client or a relevant person has been granted.

The Civil Procedure Code also provides that in the capacity of a witness in court proceedings, a lawyer cannot be required to testify if such testimony could incriminate the lawyer unless such questions are essential to the settlement of a dispute. Therefore, given that the attorney is under an obligation not to disclose any of the client's confidential information pursuant to the Penal Code, the attorney has an automatic privilege not to disclose any attorney-client communication.

The application of these sections is limited to proceedings in the civil court. Privilege under the Civil Procedure Code is not recognized and cannot be used outside the civil court.

Criminal Procedure Code

A party in a criminal proceeding cannot be required to testify or submit evidence that is confidential and that they obtain or know as a result of their profession or duty. The disclosure of confidential information, however, must be made upon the direction of the court pursuant to the Criminal Procedure Code. An exemption may also apply if such disclosure is made with the consent of the party concerned (i.e., the client). In addition, a witness in a criminal proceeding cannot be required to testify if it would result in the incrimination of that person. These provisions only apply to proceedings in the criminal court.