Yes, you can add the Team Lead to another Team as a team member.
Firstly you should remove the Team Lead as a Team Leader. Then add him as a member of another team in Salesforce.
Here is what you need to do
- Log in to Salesforce as a System Administrator
- Go to the Teams tab and remove the team lead name from Teams
- Go to the Users tab, and assign the same user to another team from the Assign to Team field. Save it.
Now the Team Lead is added as a Team Member to a Team.