Displayed content by alphabetical order
If you are creating the form with the help of a custom module, you can sort the options in the form at the time of db query before displaying them. You can do something like this.

$query=db_select('table name','n');//here your table name
 $query-&gt;fields('n', array('title'));//SELECT the fields from table 
 $query -&gt;orderBy('title', 'DESC')//ORDER BY create
 $opts=$query-&gt;execute()-&gt;fetchAllKeyed();

$form['courses'] = array(
    '#type' =&gt; 'select',
    '#title' =&gt; t('courses'),
    '#multiple' =&gt; TRUE,
    '#options' =&gt; $opts,
);