Custom Taxonomy as checkbox or dropdown

I have registered a custom tax to my CPT. On the edit screen the tax meta box appears with an autocomplete field.

Is it possible to display it as checkboxes or dropdown instead?

You probably did not set the ‘hierarchical’ argument to true in your register_taxonomy. This would mean that it defaults to false, which gives you a tag-like interface.

Add 'hierarchical' => true to your register_taxonomy.