ORDER BY LPAD(TRIM(A), 6)

WITH t AS
(
SELECT '1    ' v FROM dual
UNION ALL SELECT '2    ' FROM dual
UNION ALL SELECT '11   ' FROM dual
UNION ALL SELECT '21211' FROM dual
UNION ALL SELECT '가나1' FROM dual
UNION ALL SELECT '한123' FROM dual
)
SELECT v
--     , REGEXP_REPLACE(v, '[0-9 ]') v1
--     , TO_NUMBER(REGEXP_REPLACE(v, '[^0-9]')) v2
  FROM t
 ORDER BY REGEXP_REPLACE(v, '[0-9 ]') NULLS FIRST
     , TO_NUMBER(REGEXP_REPLACE(v, '[^0-9]'))
;