Ten nations make up the Association of Southeast Asian Nations (ASEAN) and they officially adopted the ASEAN Charter in 2009. While Article 2 of the Charter urges ‘respect for the different languages of the peoples of ASEAN,’ Article 34 makes English the sole official working language. It states, simply, that, ‘the working language of ASEAN shall be English.’ In this chapter we shall consider the implications of the role of English as the sole working language of ASEAN for diplomacy and communication among the peoples of ASEAN. Using data drawn from the Asian Corpus of English (ACE), a million-word corpus of naturally occurring spoken English as used as a lingua franca between Asian multilinguals, we shall investigate how Asians use English to discuss topics of mutual interest and importance. After some reflections on excerpts of such naturally occurring utterances, suggestions for classroom application of the insight afforded by these are offered. The chapter will conclude with proposals for necessary communication skill sets for diplomats and other professionals who wish to communicate successfully through English with Asian multilinguals. These communication skills are likely to be particularly important for people whose first language is a native variety of English, as they need to learn how English can be adapted to suit different cultures.