How can I change the drupal form action based on Radio button selected?
You can change the Form action in submit function

    function your_form_name_submit($form,&amp;$form_state){
          if($form_state['values']['radion_button_name'] == 'abc') {
         $form_state['redirect'] = url('path/to/redirect');
        }
    else{
       $form_state['redirect'] = url('path/to/redirect');
     }
}


hope this will help you!!