ISO Lead Auditor 

When the term Lead Auditor is used, it refers to an auditor who leads an ISO management system audit, usually independent of the organization being audited. A lead auditor of a Certification Body providing an independent third-party assessment of the level of compliance by an organization with the requirements of ISO 9001, ISO 14001, ISO 22000 or of another specified ISO Standard.
Becoming a lead auditor can be an exciting opportunity for you, but there may also be many questions about the process you will need to follow. So, if you want to advance your career in ISO auditing, but do not know if this is the right move for you.

If You have experience in a job that has responsibilities for understanding processes of the Quality Management System, including the possibility of performing internal audits of processes. This experience will help you to join as an auditor. 

If you don't have any prior experience, don't get disappointed, this does not mean you can not become a Lead auditor.   This will mean you need to attend the entire training, often  five days long training and you will need to write the exam. Passing the course is a mandatory prerequisite to being considered for employment as an auditor by a certification body.