Basically, any locations where you could basically unpack your bike at the airport, and get going without too many issues. Experience with many airports is they’re isolate from major trails are regular roads by major highways that bikes aren’t allowed to enter.
There is the "Lanna Kingdom" that starts in Chiang Mai, shouldn't be hard to start directly from the airport. bikepacking.com/routes/the-lanna-kingdom/ .
I'd also consider Kuala Lumpur and build my route from the pieces of existing ones.
I have a strong feeling that in SE asia you can arrange a transport on the spot even with the bike - with some communication and not much money.