As a New Testament scholar, Thomas' work has been published in the journals New Testament Studies, Novum Testamentum, Zeitschrift fur die neutestamentliche Wissenschaft, and Journal for the Study or the New Testament. He authored a study titled Footwashing in John 13 and the Johannine Community, published a collection of his essays, Ministry and Theology: Studies for the Church and Its Leaders, and wrote a commentary titled The Apocalypse: A Literary and Theological Commentary (2012) and a monograph on healing titled The Devil, Disease, and Deliverance: Origins of Illness in New Testament Thought (2011). Several other books of his include: He Loved Them until the End: The Farewell Materials in the Gospel according to John (2003); The Pentecostal Commentary on 1 John, 2 John, 3 John (2004); and The Spirit of the New Testament (2005).[4]
Thomas serves as Editor-in-Chief of the Journal of Pentecostal Theology[5] and Supplement Series, and serves as General Editor of the Pentecostal Commentary Series.[6] He is also Associate Director of the Centre for Pentecostal and Charismatic Studies, Bangor University, Wales.[7] In 1992, Ashland Theological Seminary named him Alumnus of the Year. From 1997 to 1998, Thomas served as the President of the Society for Pentecostal Studies.[8]
Thomas has also approached theological and literary study of the Book of Mormon in his 2016 book A Pentecostal Reads the Book of Mormon: A Literary and Theological Introduction.[9]
