AJAX output template thumbnail size

Hi,
I’m trying to find out how to change the post thumbnail size used in AJAX search results template. I see your code:
$image = get_the_post_thumbnail( $post->ID, 'post-thumbnail', apply_filters( 'smart_search_suggestions_image_attributes', array() ) );
And by default it takes full-size image (like 1500×800) and just scales it with CSS properties which is no good for speed and traffic. Is there any way to set up another size in template? Like ‘thumbnail’ or ‘small’?

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