This is what css is for... HTML doesn't allow for unequal padding. When you say that you don't want to use style sheets, does this mean you're OK with inline css?
<table>
<tr>
<td style="padding: 5px 10px 5px 5px;">Content</td>
<td style="padding: 5px 10px 5px 5px;">Content</td>
</tr>
</table>
You could also use JS to do this if you're desperate not to use stylesheets for some reason.