In Asia, English is used as a lingua franca (ELF; Kirkpatrick, 2010). For Thai university graduates to be successful in their future careers, being able to understand various accents with Thailand's major trading partners, particularly American, Chinese, and Japanese, seems vital. As a listening test which includes these accents is needed, the Workplace Listening Test (WLT) was developed to determine whether Thai students need more training in understanding these accents. The primary purpose of this study was to investigate effects of accented speech on workplace listening comprehension of 144 Thai undergraduate students. This investigation included three aspects. First, the study aimed to provide justification for using the WLT as a readiness measure for Thai undergraduates. Using the interpretation/use argument framework (Chapelle, Enright, & Jamieson, 2008; Kane, 2013), some substantial evidence was found to support the domain definition, evaluation, generalization, and explanation inferences. The second aspect of investigation was to examine effects of native (American) and nonnative Asian (Chinese, Japanese, and Thai) speakers' accents on listening comprehension. A three-way analysis of variance for a Latin square design was conducted. The three independent nominal variables included accents (American, Chinese, Japanese, and Thai), listening passages (eight workplace-related topics), and groups of students (Groups 1, 2, 3, and 4). The dependent interval variable was listening comprehension scores (global and local comprehension). Results indicated a facilitative effect between Thai listeners and Thai speakers. Last, previous studies suggested that accents, limited accent familiarity, and negative attitudes toward accents may hinder successful listening comprehension (e.g., Harding, 2011; Ockey & French, 2016; Kang & Rubin, 2009). This study sought to understand the roles accent familiarity and attitudes toward accents played on students' listening performances. Accent familiarity and attitudes were measured using questionnaires (Abeywickrama, 2013; Harding, 2011; Ockey & French, 2016). Using correlation analyses, results revealed that accent familiarity and attitudes were not related to listening comprehension. At present, the ability to understand various accents is part of professional competence (e.g., Harding & McNamara, 2018). This dissertation exemplified a positive step toward development of the WLT which included accents relevant to an Asian ELF workplace context in Thailand. Apart from the facilitative effect of a shared first language between speakers and listeners, results indicated that Thai undergraduates need to develop their listening competence of ELF workplace tasks. This study provided implications to inform theory, methodology, and pedagogy derived from the development of the test. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]