convert seconds to HH:MI:SS for large numbers

[PAVB]

Either you posted the wrong query or you copy/pasted the wrong error.

SQL> 
SQL> declare
  2  chk_time number;
  3  begin 
  4  chk_time := 600;
  5  select to_char(to_date(chk_time),'sssss'),'hh24:mi:ss') from dual;
  6  end;
  7  /
end;
    *
ERROR at line 6:
ORA-06550: line 5, column 55:
PL/SQL: ORA-00923: FROM keyword not found where expected
ORA-06550: line 5, column 1:
PL/SQL: SQL Statement ignored