Introduction The Thyroid-Related Patient-Reported Outcome (ThyPRO) is a new thyroid-specific quality of life patient-reported outcome measure for benign thyroid disorders. Objective The objective of this study was to investigate the face validity, internal consistency, and test-retest reliability of the Thai version of the ThyPRO (ThyPROth). Methods The translation of the ThyPRO questionnaire was performed using double forward translation, reconciliation, single backward translation, and cognitive debriefing, followed by a panel review. Five thyroid patients evaluated the face validity. The internal consistency and test-retest reliability were evaluated in 30 patients with thyroid diseases. Results The overall validity score was 3.75 (range 0-4). The Cronbach α coefficient ranged from 0.76 to 0.95, with a total coefficient of 0.97 (95% CI 0.962-0.959), indicating excellent internal consistency. The test-retest reliability coefficient ranged from 0.70 to 0.97. All values were 0.70 and above. The total reliability coefficient was 0.86 (95% CI 0.724-0.932), indicating excellent reliability. Conclusion The ThyPROth was found to be valid and to exhibit good internal consistency and test-retest reliability. The questionnaire is ready for implementation in the assessment of health-related quality of life in Thai patients with benign thyroid diseases.