Our knowledge of the history of Siamese literature before 1767, when Ayudhya was destroyed by the Burmese, is questionable, as the task of ascribing dates and authorship is made chancy by the modes of preservation, the later reconstruction of works destroyed, and the weight of an unyielding tradition. A prominent and original poem, one of few classical poems recognizable as a tragedy, the Lilit Phra Lo has been credited, for some obscure reason, to the time of King Naray (1656-1688). This paper, based on clues found mainly in the Ayudhya Annals and on an analysis of the poem’s versification, submits an earlier date – late 15th or early 16th century – and ascribes it to a son of King Boromotraylokanat (1448-1488). It concludes that the Golden Age of classical Siamese literature should be dated from the times of kings Boromotraylokanat, Boromorachathirat iii (1488-1491), and Ramathibodi ii (1491-1529), contrary to the broadly accepted view (second half of the 17th century).