Thailand follows the first-to-file rule. To obtain protection of a mark in Thailand, a registration must be obtained from the Department of Intellectual Property (DIP) initiated by filing an application with the Trademark Office.

Nevertheless, the “owner” of an unregistered mark or senior user is not without recourse. It cannot sue before the Thai courts to prevent the junior user from using the identical or confusingly similar trademark, but an opposition or cancellation action is available and may prevent third parties from otherwise registering an identical or confusingly similar trade mark.

During the publication period or any time after registration, the senior user or unregistered trade mark owner may file an opposition or cancellation action against the registration of an identical or similar mark based on the ground that it has a better title to the mark. Bad faith on the part of the junior user may also be alleged. Simultaneous to filing the opposition, it is strongly recommended that the senior unregistered user also file an application with the Trademark Office.

To support its claim that the senior unregistered user has a better right, it is important to emphasize the prior use of the mark in Thailand and elsewhere. Evidence may include photocopies of all registration certificates outside Thailand. In addition, the senior user needs to show long-time consistent use of the mark, such as samples of advertising materials, marketing materials, product brochures and sales information dating prior to the filing date of the junior user.

In the case of The Wellcome Foundation Co. Ltd. v. Dairy Management., the court ruled that the person who can prove prior use to the trade mark has a better right to register the mark, especially when it has been registered and known in other countries and there is evident bad faith on the part of the party who uses the same. The similarity of the trade mark might then lead to confusion of the public as to the real origin of the goods.