Upvote:1
The situation described is pretty strange. If you bought original tickets through the Expedia, who is an online travel agent. The Expedia is a ticket issuer, and the airline itself can't split the reservation or charge money for it. To the best of my knowledge, all changes to the reservation can only be made through the agent who issued the ticket.
In the situation when:
Expedia can't do anything because it has nothing to do with the changing of the reservation. The airline is responsible for the issue, and you can only send a complaint to the airline. The Thai Lion Air seems to have mediocre support, so I am sure they will ignore the complaint. The only reasonable way to get the compensation is to ask the chargeback for the money you paid to split the reservation.