This paper reports on an analysis of environmental discourse, or green discourse, in the linguistic and geosemiotic landscape of a Thai university. The overwhelming majority of green discourse signs at the university are in English and where they are bilingual (Thai and English), they tend to contain English in the preferred position. The language usage on the signage is also shown to be related to the sociolinguistics of globalization (Blommaert 2010) in terms of scale, indexical order, and polycentricity. These data are triangulated with data collected from walking interviews with students. The literature on ecolinguistics, the ecology of language and green discourse are reviewed within the context of the present study. The analysis focuses upon the geosemiotics (Scollon and Scollon 2003) of green discourse and how such discourse reflects patterns of the sociolinguistics of globalization.