If you move the whole block of "who's viewing" (shown below) to the top of your threads by editing SHOWTHREAD then it will move with it.
HTML Code:
<!-- currently active users -->
<if condition="$show['activeusers']">
<table class="tborder" cellpadding="$stylevar[cellpadding]" cellspacing="$stylevar[cellspacing]" border="0" width="100%" align="center">
<tr>
<td class="tcat" colspan="2">
<phrase 1="$totalonline" 2="$numberregistered" 3="$numberguest">$vbphrase[users_viewing_this_thread_x_y_z]</phrase>
</td>
</tr>
<tr>
<td class="alt1" colspan="2">
<span class="smallfont">$activeusers</span>
</td>
</tr>
</table>
</if>
<!-- end currently active users -->