Purpose <p>The precise anatomy of the anterior spinal artery is clinically important for surgical and endovascular procedures. Therefore, this study aims to investigate variations in the anterior spinal artery, including its origin, morphometry and formation patterns, in the Thai population.</p> Methods <p>Twenty-six adult cadaveric brains (52 sides) were examined. In each brain, the site of origin, external diameter and formation patterns of the anterior spinal artery were recorded. The distances between the site of origin and both the vertebrobasilar junction and the posterior inferior cerebellar artery were measured on the left and right sides.</p> Results <p>The anterior spinal artery most commonly originated from a posteromedial (62.5%), followed by a medial origin (37.5%). A classification of anterior spinal artery morphology in Thai population was proposed, comprising three main types (I to III) and subtypes (Ia to Ic, IIa to IIc). Type III (independent bilateral anterior spinal artery) was most frequent (34.5%), followed by Type Ia (23.6%) and Type IIa (15.4%). The left vertebral artery showed a significantly larger diameter (<i>p</i> &lt; 0.05). Several arterial diameters demonstrated strong positive correlations, all statistically significant (<i>p</i> &lt; 0.05).</p> Conclusion <p>The present study delineates the origin and formation patterns of the anterior spinal artery in the Thai population, demonstrating type III as the predominant configuration. These findings provide a robust foundation for subsequent investigations. Comprehensive knowledge of anterior spinal artery anatomical variation is critical for reducing the risk of vascular complications during surgical interventions.</p>