How long do you spend in Asia? If you want to travel all places in Asia, you need 3-4 months to travel. You can visit Vietnam, Thailand and Cambodia. You can read more itinerary at https://www.vietnamtourbooking.com/en/
You can't Interrail in Asia, it's a European thing only.
If you just mean getting a load of trains to places then it's probably easily do-able. I've got no experience with Asia but I've been Interrailing before so AMA I guess.