Remove WYSIWYG Editor for Custom Post Type

functions.php

<?php
/**
 * Remove the text-editor from CPT
 */
function disable_wysiwyg_for_CPT( $default ) {
	global $post;

	if ( 'CPT' == get_post_type( $post ) ) {
		return false;
	}

	return $default;
}
add_filter( 'user_can_richedit', 'disable_wysiwyg_for_CPT' );