What do you imagine when you hear the word Solo Trip.
A bike , a backpack and you. Dude destination is just a variable option u just need to get out. You can go trekking with random groups , or go andaman dive in deep into ocean explore the under water world.
See the fact is there are loadz of places u can visit you just need to find out where do you want to go.
stay happy.
Depends on your preference whether you like mountain / beaches / history.
I went to Cambodia for solo trip last december. Check out my blog on that.
My suggestions for you - Nepal / Bhutan / Vietnam / Cambodia / Bali