One of the features of the growing prominence of English across the globe is the proliferation of English-medium instruction (EMI) programmes at all levels of education, driven by a neoliberal agenda which places a disproportionate value on English over other languages. While this spread has primarily affected more developed, urban contexts, EMI has also started to spread beyond the borders of large cities and into peripheral, rural areas, including those where minority languages are used. There is at present, however, a sparsity of research on how the introduction of EMI impacts the often delicate language ecology in such contexts. This paper presents the results of a study of how EMI policy was implemented at a primary school in the Deep South of Thailand, a region where the majority of the population speak Malay as their L1. The findings of this research, drawn on the basis of interviews, focus groups and classroom observations, highlighted the existence of a hierarchical linguistic ecology in which English and Thai, the international and national language, were privileged over the local language, owing both to their dominant position in official language policy and the attitudes of local policy arbiters.