Hi lipearibeiro,
This is possible but only with a custom implementation. You can get the groups using for example the core function:
https://github.com/itthinx/groups/blob/master/lib/views/class-groups-shortcodes.php#L381
and then render the results with a select field.
Last but not least, you need to also decide and implement what should happen with the selected group, once the form is submitted. For example, if the user is authenticated and should join the selected group, then you can take ideas from:
https://github.com/itthinx/groups/blob/master/lib/views/class-groups-shortcodes.php#L462
Kind regards,
George