Currently, the role of English language has changed from being a language used among native English speakers (NESs) to being a language spoken by people of various backgrounds or known as English as a lingua franca (ELF). This phenomenon has affected different aspects of global English usage and users across the world. However, in Thailand, this issue does not seem to be taken into account with regard to English language teaching (ELT) and learning practices as different ELT stakeholders continue to conform to traditional teaching methods related to NESs. This action is reflected in an English language ideology called 'native speakerism' which has long been entrenched in Thai society. It has repeatedly caused different problems for both Thai teachers and students of English language until the present day. This review article aims to demonstrate the impacts of the native speakerism ideology on Thai teachers and students of English language in the period of English as a global lingua franca. The article begins with an explanation of how the changes of role and status of English challenge traditional perspectives of English language and how the ELT industry around the world, including in Thailand, should adapt to such changes. Then, the article gives brief conceptualizations of native speakerism and its effects on English teachers and students. Finally, it moves on to discuss the native speakerism ideology in Thailand and reports different negative effects of native speakerism on Thai teachers and students of English language.