You can undo the seam in different ways:

1) From the front as shown in the photo on the previous step. 2) From between the fabrics, by pulling gently on the pocket seam to reveal the thread underneath. 3) From the inside if the jeans.

Choose whichever works best for you. Consider, where is the thread most visible? Where is it easiest to pick up the thread with the ripper or scissors and cut it? Often, alternating is needed.