I will be flying to Katmandu, from there I hope to trek a bit in the Himalayas then slowly make my way down to Thailand by January. Have no set plans, how feasible is it to bus/train/ hitch through any of these countries as well as burma, and India? Visas/ costs/must dos/ must donts/any advice would be greatly appreciated!
You've given yourself heaps of time. Bus/train would definitely be the way I'd be going. Check out East India/Bangladesh if you get a chance. They're so little travelled, but there's some amazing stuff to see. I will say you're going to struggle to get into Myanmar overland. Things are opening up but the land borders are kept pretty tight. Flying into Yangon is going to be your best bet.
If you've got any specific questions let me know, happy to help out as best I can. about 3 years ago