Sorry, but I think all my backup plans are still valid. You can fly from REP to Laos or Vietnam, assuming Thailand flights are shut down. You can get to PNH and fly from there, or get a Lao or Vietnamese visa easily to do a border crossing.

By air, Vietnam does allow transit to another outbound international flight without having a Vietnamese visa. I know of people who have done this, at least at SGN. Laos normally offers VOA at its airports that have international incomings.