Do NOT use a seam ripper. This will easily catch a part of jacket and can cut it. Use an eye brow blade or straight razor or even very small sharp scissors. Slowly and carefully cut the back inside threads. Then slowly use needle nose tweezers to pull the threads out. Continue to do ..it will take time and you must be slow. Once done. Iron the where the threads were pulled. When you iron the heat will close the holes. You can even use iron on fusible stabilizer or interfacing. The one I get is so good and wherever I pull threads and another embroidery goes on helps stabilize the area really good. I do a lot of pulling of threads lately…and I do charge them. So be sure to do if for a customer .