[Plugin: NextGEN Gallery] Thumbnail doesn't show

Hello,

Im using the BangkokPress theme and I just installed NextGEN gallery and Im running into a problem. The post thumbnail don’t show up on the homepage. Probably because the theme grabs the default media library. How can I change this? Does anyone know?

I guess I should add/edit code here:

// Print blog thumbnail
	function print_gdl_blog_thumbnail( $thumbnail_type, $item_size ){

			if( $thumbnail_type == "Image" || empty($thumbnail_type) ){

				$thumbnail_id = get_post_thumbnail_id( get_the_ID() );
				$thumbnail = wp_get_attachment_image_src( $thumbnail_id , $item_size );
				$alt_text = get_post_meta($thumbnail_id , '_wp_attachment_image_alt', true);
				if( !empty($thumbnail) ){
					echo '<div class="blog-thumbnail-image">';
					echo '<a href="' . get_permalink() . '"><img src="' . $thumbnail[0] .'" alt="'. $alt_text .'"/></a></div>';
				}

			}

Can anyone help me?

Thanks