You can make a new method in the employee that returns the internal notes and attachments. If you search for the employee record you can call this method to get the data from anywhere.

def get_employee_notes_attachments(self):
    return employee.internal_notes, employee.attachments

and call it like this:

employee = self.env['employee.model'].search([('id', '=', employee_id)])
notes, attachments = employee.get_employee_notes_attachments()

I don't know what odoo version you use, this answer would be for v8 or newer.