+1-888-413-6950 Passengers occasionally go through the check-in process and neglect to upgrade their seats. In this case, you can upgrade your seat after check-in to acquire the best available seat through Thai Airlines' seat upgrade policy. On the Thai Airways or WingsTravo websites, you can get all the information on the seat upgrades and learn everything there is to know. Along with all the details, you can contact the Thai Airlines customer care department to inquire about seat upgrades.