This paper examines the linguistic landscapes of 15 Bangkok neighbourhoods to explore questions of language contact, language mixing and language dominance. It provides a linguistic framework for analysis of types of codemixing. It highlights the importance and influence of English as a global language. It examines the signs from government sources versus those from the private sector. It also reveals the extent of linguistic diversity in a large metropolitan area like Bangkok by a comparison of various neighbourhoods. Moreover it offers evidence of a shift from Chinese to English as the major language of wider communication in the city. From a linguistic perspective, the paper documents the influence of English on the development of Thai, not just in the form of lexical borrowing, but also in the areas of orthography, pronunciation and syntax. At the same time, the study provides evidence of a nascent Thai variety of English. At the theoretical level, this study calls into question the boundaries of a speech community and even what constitutes a language itself. From a more applied perspective, the data presented raise questions about the effects of the pervasiveness of English in the linguistic landscape of Bangkok on the language proficiency, both Thai and English, of its youngest citizens. (Contains 1 table, 7 figures and 5 notes.)