Associate membership

I am a member of a WELS church. Can I be an associate member at another synod Lutheran Church while keeping my membership intact at my WELS church?

No. Such a situation is not workable. With church membership, people commit themselves to the doctrine and practice of that church. If multiple memberships were allowed, people would be committing themselves to different doctrines and practices.

Membership in more than one church presents many challenges. One of the most practical and serious deals with the spiritual care of the individual, especially if church discipline were involved (Matthew 18:15-20). Confusion and/or disagreement over which pastor is the primary shepherd of the individual would be a natural result.