Just use the size attribute:
<select name="sometext" size="5">
<option>text1</option>
<option>text2</option>
<option>text3</option>
<option>text4</option>
<option>text5</option>
</select>
To clarify, adding the size attribute did not remove the multiple selection.
The single selection works because you removed the multiple="multiple" attribute.
Adding the size="5" attribute is still a good idea, it means that at least 5 lines must be displayed. See the full reference here