All your son need is his passport, a photocopy of his passport (it can be useful sometimes) and his flight ticket.
In Bangkok, everybody can speak thai: it is easy.
Ms, Ingsacha, did you book the flight Bangkok-Manila and Manila-Cebu with the same airplane company? If yes, when he will check-in his luggage, your son must ask that his luggage will be sent directly to Cebu: It will be easier for him (no need to get his luggage in Manila and check-in again for Manila to Cebu).
In Manila:
- Make sure the arrival from Bangkok and departure for Cebu is in the same airport and same terminal.
- Make sure he arrives in Manila at least 2 hours before the departure for Cebu.
- Teach your son the following English words: "gate" - "boarding time". That is all he needs. In case of problem, you don't even need to talk:show your flight ticket to anyone, they will help and guide.
In Cebu: my staff will be at the airport with a signage "EV ACADEMY". No more worries.