A bit late now but maybe it helps anyway. I solved it by adding the thickbox div to the 'admin_footer' via filter. If you do so the code is outside the general form.
Ok so here is the code how i added a form:
add_filter('admin_footer-edit.php', 'expose_form'); function expose_form(){
?>
Andruck wählen
Andrucken Seite Titelseite andrucken- Graustufenbilder
</td>
</tr>
<tr>
<td><input type="checkbox" name="detailpage" value="detailpage" checked="true"></td>
<td><label for="titlepage">Detialsseite andrucken</label>
<ul>
<li><input type="radio" name="adaptiveheight" value="adaptive" checked="true"> Adaptive Zeilenhöhe</li>
<li><input type="radio" name="adaptiveheight" value="fixed"> Fixe Zeilenhöhe</li>
</ul>
</td>
</tr>
<tr>
<td><input type="checkbox" name="mappage" value="mappage" checked="true"></td>
<td><label for="titlepage">Karte andrucken</label></td>
</tr>
<tr>
<td><input type="checkbox" name="textpage" value="textpage" checked="true"></td>
<td><label for="titlepage">Textseiten andrucken</label></td>
</tr>
<tr>
<td><input type="checkbox" name="picpage" value="picpage" checked="true"></td>
<td><label for="titlepage">Bildseiten andrucken</label></td>
</tr>
<tr>
<td><input type="checkbox" name="agbpage" value="agbpage" checked="true"></td>
<td><label for="titlepage">AGB Seite andrucken</label></td>
</tr>
<tr>
<td><input type="checkbox" name="docpage" value="docpage" checked="true"></td>
<td><label for="titlepage">Mieterliste andrucken</label></td>
</tr>
<tr>
<td><input type="text" name="imagequality" value="30"></td>
<td><label for="imagequality">Bildqualität %</label><p>100 = Originalbilder 0 = kleinste Dateigröße</p></td>
</tr>
<tr>
<td colspan="2"> <input type="submit" class="button-primary" value="genereieren"></td>
</tr>
</form>
</table>
</div>
<div class="ajaxloading">
<div class="spinner"></div>
</div>