To develop an internal audit plan that aligns with ISO 9001 standards, focusing on the most critical areas for compliance, you should follow these steps:

1. **Conduct a GAP Analysis**: Determine the extent to which your organization already complies with ISO 9001:2015. This will help identify areas that need attention.

2. **Establish a Project Plan**: Define activities, deadlines, and other relevant information needed to address the gaps identified in the GAP analysis.

3. **Plan the Audit Schedule**: Determine the frequency and timing of audits based on the importance of the processes and previous audit results.

4. **Define Audit Criteria and Scope**: Clearly outline what will be audited, including the specific ISO 9001 clauses and internal procedures.

5. **Ensure Auditor Competence**: Make sure your internal auditors are trained and competent, and ensure they do not audit their own work to maintain objectivity.

6. **Conduct the Internal Audit**: Follow a structured process to evaluate compliance with ISO 9001 requirements, focusing on the most complex processes and those with a higher probability of nonconformities.

7. **Report and Follow-up**: Document the audit findings, communicate them to relevant management, and ensure corrective actions are taken for any nonconformities found.

8. **Management Review**: Conduct a management review to assess the effectiveness of the QMS and the audit process.

By following these steps, you can ensure that your internal audit plan is comprehensive and aligned with ISO 9001 standards, focusing on critical areas for compliance.