SELECT 
  cscart_products_categories.product_id, 
  GROUP_CONCAT(
    IF(
      cscart_products_categories.link_type = "M", 
      CONCAT(
        cscart_products_categories.category_id, 
        "M"
      ), 
      cscart_products_categories.category_id
    )
  ) AS category_ids, 
  product_position_source.position AS position 
FROM 
  cscart_products_categories 
  INNER JOIN cscart_categories ON cscart_categories.category_id = cscart_products_categories.category_id 
  AND cscart_categories.company_id = 3 
  AND (
    cscart_categories.usergroup_ids = '' 
    OR FIND_IN_SET(
      0, cscart_categories.usergroup_ids
    ) 
    OR FIND_IN_SET(
      1, cscart_categories.usergroup_ids
    )
  ) 
  AND cscart_categories.status IN ('A', 'H') 
  LEFT JOIN cscart_products_categories AS product_position_source ON cscart_products_categories.product_id = product_position_source.product_id 
  AND product_position_source.category_id = 755 
WHERE 
  cscart_products_categories.product_id IN (
    617, 616, 625, 606, 622, 609, 603, 638, 
    608, 627, 620, 619, 601, 9480, 624, 605, 
    9476, 642, 604, 644, 602, 630, 632, 640, 
    629, 646, 635, 641, 631, 636
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00170

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE cscart_products_categories range PRIMARY,pt,product_id_idx,category_id_idx,product_category_idx,category_product_idx product_id_idx 3 90 Using index condition
1 SIMPLE product_position_source eq_ref PRIMARY,pt,product_id_idx,category_id_idx,product_category_idx,category_product_idx PRIMARY 6 const,mahm3t_cs443.cscart_products_categories.product_id 1
1 SIMPLE cscart_categories eq_ref PRIMARY,c_status,p_category_id,idx_category_id PRIMARY 3 mahm3t_cs443.cscart_products_categories.category_id 1 Using where

Result

product_id category_ids position
601 775
602 775
603 775
604 775
605 775
606 775
608 775
609 775
616 792
617 792
619 801
620 801
622 801
624 801
625 801
627 819
629 819
630 819
631 819
632 819
635 819
636 819
638 815
640 815
641 815
642 815
644 815
646 815
9476 775
9480 792