SQL> select * from mhe_foo
  2    order by thevalue ASC
  3  /

THEVALUE
----------
FS
FT
SF
dm
hdus
hf
hr
hrecy
hrub
hsoft
hw

SQL> SELECT   thevalue
  2      FROM (SELECT thevalue
  3                 , RANK () OVER (ORDER BY thevalue ASC) rn
  4              FROM mhe_foo)
  5  ORDER BY DECODE (GREATEST (thevalue, 'dm'), thevalue, rn, 'dm', rn * 100)
  6  /

THEVALUE
----------
dm
hdus
hf
hr
hrecy
hrub
hsoft
hw
FS
FT
SF

11 rows selected.