Add the following snippet in template.php of your active theme;
<?php
function THEMENAME_theme($existing, $type, $theme, $path) {
return array(
'article_node_form' => array(
'arguments' => array('form' => NULL),
'template' => 'node--add--article',
'render element' => 'form',
),
);
}
?>
Then create a template file called node--add--article.tpl.php (same as the 'template' field in template.php.)
This is node--add--article.tpl.php:
<table >
<tr>
<td><?php print drupal_render_children($form['field_1']); ?></td>
<td><?php print drupal_render_children($form['field_2']); ?></td>
<td><?php print drupal_render_children($form['field_3']); ?></td>
</tr>
</table>
<?php print drupal_render_children($form); ?>
Now Clear Cache and see the result.