Tienes que poner la parte de tu where declaración a la clase:
select t1.month,count(t2.emp_id) as count
from Table1 t1
left outer join Table2 t2 on t2.from_date between t1.start_date and t1.end_date
and t2.org_id=46 group by t1.month
Si no lo haces tienes un inner join
