Definition and validity criteria of the electronic signature

Electronic signature is defined by Section 4 of the ETA as:

“Letters, characters, numbers, sounds or any other symbol created electronically and affixed to a data message in order to establish a link between a person and a data message for the purpose of identifying the data message signer and demonstrating approval of the information contained in the data message in question.”

Section 9 of the ETA considers an e-signature to be a signature that meets both of the following criteria:

➤ A signature method that identifies the signer and indicates that he or she has approved the information contained in the electronic document as his or her own
➤ The method is reliable and appropriate for the purpose for which the electronic document was generated or sent, taking into account the circumstances surrounding the act, or the agreement of the parties

Section 26 of the ETA considers as a Reliable Electronic Signature, a signature that meets the following criteria:

➤ The signature creation data are, taking into account the context in which they are used, related only to the signatory and no one else
➤ The signature creation data were, at the time of creation of the e-signature, solely under the control of the signatory and no one else
➤ Any alteration of the electronic signature, since its creation, must be detectable
➤ In the event that a legal obligation requires the e-signature to ensure the integrity of information, any alteration of that information made since the document was signed must be detectable

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Acts for which an electronic signature can be used

In principle, according to the ETA, it is possible to use this type of signature for civil and commercial acts, except those expressly excluded by law.

Two categories of acts where e-signature is possible must be distinguished: those where no formalism is required by law and those where a signature and a writing are required.

For some contracts no formality is required by Thai law, in this case it is quite possible to use an e-signature, without the criteria provided in section 26 of the ETA for a Reliable Electronic Signature necessarily being met. Examples of acts where no formalism is required:

Employment contract
Non-disclosure agreement
➤ Software license
➤ Transaction between consumers (C to C)

For other acts, it is generally necessary to use a writing signed by the parties, in which case the act cannot lose its legal force for the sole reason of having used an e-signature.
However, the validity of the signature can always be challenged in court, which requires compliance with the criteria of Section 9 and 26 of the ETA, in order to have a Reliable Electronic Signature, which will have a better probative force in case of conflict.

Acts for which electronic signature is prohibited

Thai law prohibits the use of e-signature and electronic document for deeds and transactions relating to family and inheritance (Royal Decree Prescribing Civil and Commercial Transaction wich are Exempted from the Application of th Law on Electronic Transactions, B.E. 2549 (2006)).

In addition, in general, acts requiring registration with the competent authorities (Civil and commercial code). Some examples:

➤ Contracts for the sale of real estate
➤ Contracts for the lease of real estate for a period exceeding three years
➤ Mortgage contract

The use of timestamping

Timestamping is a system that makes it possible to preserve proof of the existence of a document and its contents at a given date. The term “proof” indicates the fact that no one, not even the owner of the document, can modify the timestamping certificate. The use of a Certification Authority, and therefore a trusted third party, makes it possible to secure the e-signature in the event of a dispute.


The electronic signature represents an undeniable advantage in terms of speed and simplification, however, before using it, it is advisable to check that it is authorized for the act envisaged and, if this is the case, to ensure that it meets the criteria set out in the ETA. As an e-signature can always be challenged in court, it is advisable for the most important acts to use timestamping via a Certification Authority.

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