Changing default thumbnail image of WooCommerce product

functions.php

<?php

/**
 * Change the placeholder image
 */

add_filter('woocommerce_placeholder_img_src', 'custom_woocommerce_placeholder_img_src');
function custom_woocommerce_placeholder_img_src( $src ) {
    $upload_dir = wp_upload_dir();
    $uploads = untrailingslashit( $upload_dir['baseurl'] );
    // replace with path to your image
    $src = $uploads . '/2020/03/default-product-image.png';
    return $src;
}

/*For thumbnail*/

add_filter('woocommerce_placeholder_img', 'downloadclub_woocommerce_placeholder_img', 10, 3);
function downloadclub_woocommerce_placeholder_img($image_html, $size, $dimensions){
	$image      = wc_placeholder_img_src( $size );
    //replace image url
	$image_html = '<img src= "http://site.com/wp-content/uploads/2020/03/default-product-image-2.png"' . esc_attr( $image ) . '" alt="' . esc_attr__( 'Placeholder', 'woocommerce' ) . '" width="' . esc_attr( $dimensions['width'] ) . '" class="woocommerce-placeholder wp-post-image" height="' . esc_attr( $dimensions['height'] ) . '" />';

	return $image_html;
}