Are Paul's letters in the New Testament arranged in the order he wrote them?
No. Paul's letters are not arranged in the New Testament in the chronological order he wrote them. They appear in the exact order the Holy Spirit intended, and that order is consistently preserved in manuscripts. Thessalonians was written first, then Galatians, Romans, Corinthians, and later letters.
Les explains that Paul's letters are not in chronological order, yet they are arranged in the exact order the Holy Spirit wanted. He notes that in New Testament manuscripts available in museums and libraries, Paul's letters never appear in a different order; they have always been the same, unlike the Gospels or the little letters at the back, which sometimes vary. The chronological sequence was Thessalonians first, probably Galatians, then Romans, Corinthians, Ephesians, Philippians, Colossians, then first and second Timothy and Titus. Galatians was written about two years before the Corinthian letters.