woocommerce functions.php code that disables all email notifications for guest customer order with "cheque" payment gateway.

woocommerce-function.php

/**
 * Code goes in functions.php or a custom plugin.
 */

/**
 * @snippet       Disable Order notification For Specific Payment Gateway
 * @author        Ashiqur Rahman
 */


add_action( 'woocommerce_email', 'disable_emails' );

function disable_emails( $email_class ) {

   if ( ! is_admin() ) {
	
      $selected_payment_method_id = WC()->session->get('chosen_payment_method');
	   
      if ( $selected_payment_method_id = 'cheque' ) {

        // New order emails
        remove_action( 'woocommerce_order_status_pending_to_processing_notification', array( $email_class->emails['WC_Email_New_Order'], 'trigger' ) );
        remove_action( 'woocommerce_order_status_pending_to_completed_notification', array( $email_class->emails['WC_Email_New_Order'], 'trigger' ) );
        remove_action( 'woocommerce_order_status_pending_to_on-hold_notification', array( $email_class->emails['WC_Email_New_Order'], 'trigger' ) );
        remove_action( 'woocommerce_order_status_failed_to_processing_notification', array( $email_class->emails['WC_Email_New_Order'], 'trigger' ) );
        remove_action( 'woocommerce_order_status_failed_to_completed_notification', array( $email_class->emails['WC_Email_New_Order'], 'trigger' ) );
        remove_action( 'woocommerce_order_status_failed_to_on-hold_notification', array( $email_class->emails['WC_Email_New_Order'], 'trigger' ) );

        // Processing order emails
        remove_action( 'woocommerce_order_status_pending_to_processing_notification', array( $email_class->emails['WC_Email_Customer_Processing_Order'], 'trigger' ) );
        remove_action( 'woocommerce_order_status_pending_to_on-hold_notification', array( $email_class->emails['WC_Email_Customer_Processing_Order'], 'trigger' ) );

      }

   }

}