ABSTRACT Introduction: Asian patients often seek to address lower facial aging through clinical interventions that increase anterior projection and jawline contouring. The DefinisseTM (also known as Happy LiftTM) thread lift treatment uses barbed absorbable threads to suspend tissues and induce biostimulation. We evaluated the efficacy and safety of absorbable barbed threads for lower facial reshaping in Thai patients. Methods: This prospective, evaluator-blinded study enrolled 27 Thai patients diagnosed with mild to moderate facial laxity. Patients underwent thread implantation along the mandibular angle with one of two double needle thread lengths (12 and 23 cm) to create a ‘‘J stitch’’. Primary outcome was the clinical improvement in facial laxity as graded by two blinded dermatologists at baseline, immediately after treatment, and at 1 week and 1, 2, 3, 6, and 12 months follow-up. Objective measurements included volume in the jawline, nasolabial folds, and submental area. Patients’ selfassessment scores and adverse reactions were recorded. Results: Of the 27 patients recruited to the study, 25 (92.6%) attended all follow-up visits. Clinical improvement of facial laxity was observed immediately after thread implantation. There was significant volume improvement in the jawline, nasolabial folds and submental area at almost all follow-up visits (p \ 0.007), with most patients (51.9%) reporting excellent lifting effect as early as the 1 week follow-up visit. All adverse reactions were mild and resolved spontaneously without any medical intervention. Conclusion: Implantation of absorbable barbed threads is a safe and effective treatment for facial rejuvenation in Thai patients. Long threads (23 cm) showed a slight superiority to short threads (12 cm) in terms of face-lifting efficacy, which suggests the benefit of additional barbs in tissue suspension and biostimulation. The disadvantage of absorbable threads is that their visible lifting effects are not as longlasting as those of non-absorbable ones, since they are reabsorbed from 6 months onwards. Trial registration: ClinicalTrials.gov identifier: TCTR20210415001. This clinical trial was retrospectively registered 12 April 2021.