Embed autocomplete textfield in a block
Your block content should look like this:

function cse_block_content($which_block){
  switch ($which_block) {
    case 'cse_search':
      drupal_render(drupal_get_form('my_custom_form'));
    break;

    default:
    break;
  }
}

function my_custom_form($form, &amp;$form_state) {
  $form['cse_search'] = array(
      '#title' =&gt; t('CSE Autocomplete TEST!'),
      '#type' =&gt; 'textfield',
      '#autocomplete_path' =&gt; 'cse/google/autocomplete',
  );

  // Adds a simple submit button that refreshes the form and clears its
  // contents. This is the default behavior for forms.
  $form['submit'] = array(
      '#type' =&gt; 'submit',
      '#value' =&gt; 'Save',
  );

  return $form;
}