This article considers the problem of parallel importation of patented products in Thailand in the light of the ASEAN Economic Community (AEC). One of the objectives of the AEC is to promote the free movement of goods and a single market within the Southeast Asia region. But, the exhaustion provision in section 36(7) of the Thai Patent Act 1979 makes it difficult for Thailand to achieve such an objective because it is unclear whether this provision is applied as national exhaustion or international exhaustion. Also, this exhaustion provision can only apply to the petty patent and the patent for invention, but cannot apply to the design patent, so the design patent owner can prevent parallel importation of products embodying the registered design from other ASEAN countries into Thailand. In order to achieve the AEC objective, this article argues that a regional exhaustion approach like that of the EU is appropriate for Thailand, but the wording of the current exhaustion provision does not support the application of a regional exhaustion approach. Hence, this article suggests that changes should be made to several provisions in the Thai Patent Act 1979 in order to make them compatible with the regional exhaustion approach. Such a change should ensure that the exhaustion provision can be applied to the design patent. Also, the proposed change should ensure that if the products are manufactured by the holder of a compulsory licence in another country and imported into Thailand without the consent of the patent owner, then the patent owner in Thailand should be able to prevent it. The additional legal measure, which provides a means of access to the complaints procedures of the relevant safety authorities in the circumstance where the patented products imported from other ASEAN countries are not safe, should be introduced. Also, a change should be made to some border measures provisions in order to allow such provisions to apply where the imported products infringed the patent right in the same manner as they apply in the context of trademark and copyright.