SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    336, 338, 337, 339, 340, 341, 342, 343, 
    344, 345, 346, 347, 348, 335
  ) 
  AND category_id != 264

Query time 0.00042

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "23.29"
    },
    "table": {
      "table_name": "cscart_categories",
      "access_type": "ALL",
      "possible_keys": [
        "PRIMARY",
        "parent",
        "p_category_id"
      ],
      "rows_examined_per_scan": 98,
      "rows_produced_per_join": 25,
      "filtered": "26.53",
      "cost_info": {
        "read_cost": "18.09",
        "eval_cost": "5.20",
        "prefix_cost": "23.29",
        "data_read_per_join": "87K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "((`danishecarter_25_march`.`cscart_categories`.`parent_id` in (336,338,337,339,340,341,342,343,344,345,346,347,348,335)) and (`danishecarter_25_march`.`cscart_categories`.`category_id` <> 264))"
    }
  }
}