OBJECTIVES: Myofascial pain characterized by myofascial trigger point (MTrP) is a common cause of musculoskeletal pain and the main cause of neck and shoulder pain in the working population. Thread embedding acupuncture (TEA) is a new modality that can provide long-term stimulation to prolong the same therapeutic effect as conventional acupuncture. This study aimed to determine the effect of TEA therapy on pain score, neck disability index (NDI), and pressure pain threshold (PPT) for myofascial pain in the upper trapezius muscle. METHODS: The research design in this study was a double-blind, randomized clinical trial. This study with 44 research subjects was divided into TEA group (n=22) and sham TEA group (n=22). Both groups will receive TEA therapy once using CARA brand monofilament polydioxanone thread 29Gx50 mm or sham TEA (thread removed) at one trigger point in the upper trapezius muscle which will be followed-up on 3 days, 1 week, 4 weeks, and 8 weeks post-therapy. RESULTS: Both groups experienced significantly reduced pain intensity and disability, also increased PPT at 3 days, 1 week, 4 weeks, and 8 weeks post-therapy (p<
0.001). TEA therapy had better effectiveness in improving pain intensity at 4 weeks (p=0.007) and 8 weeks post-therapy (p=0.004), NDI scores at 8 weeks post-therapy (p=0.004), and PPT at 4 weeks (p=0.04) and 8 weeks post-therapy (p=0.002) compared to sham TEA. CONCLUSIONS: TEA reduced pain intensity and disability, and increased PPT for patients with myofascial pain in the upper trapezius muscle.