<p>Accurate detection of noncredible symptom reporting is critical for procedural fairness, the integrity of forensic psychological assessment, and informed legal decision-making. The Symptom Validity Test–Thai (SVT-Th), originally developed in 2019 and comprising 57 items, warrants revision to strengthen its conceptual and psychometric foundations. In Study 1, we revised and evaluated the SVT-Th-Revised using a large field dataset and derived a provisional cutoff via a forensic simulation design. The original scales were mapped onto two detection strategies: the Unlikely Detection Strategy (UDS) and the Amplified Detection Strategy (ADS). Confirmatory factor analysis (<i>n</i> = 1,173) supported a hierarchical structure, yielding a 49-item version with excellent model fit. The model represents noncredible symptom reporting as a higher-order construct indexed by UDS and ADS, which may support profile-based interpretation in forensic and disability-related assessments (FDRA). In Study 2, we used a newly collected simulation sample (<i>n</i> = 233); ROC analysis indicated outstanding classification accuracy under simulation conditions (AUC = 0.99), with an optimal cutoff of ≥ 58 yielding 99.20% sensitivity and 96.30% specificity. We applied this cutoff to Study 1 naturalistic datasets (<i>n</i> = 752), observing failure proportions of 2.20% in an incarcerated sample and 24.30% in a forensic clinical sample. Given that independent criterion indicators of response validity were unavailable in Study 1, these transported-cutoff estimates are considered descriptive rather than field estimates of specificity or false-positive rates. Overall, the SVT-Th-Revised shows promising potential as a locally developed symptom validity measure, underscoring the need for continued field-based cross-validation using independent criterion indicators.</p>