I understand that for foreigners it is'nt possible to travel overland into and from Myanmar. I am looking to travel/backpack from the TransMongolia Expres into China and onwards into SE Asia. Is it true: can you only fly in? Or can you possibly take a train?
And: if it is true: does anyone have suggestions for cheap flights from the region?
You cannot take a train to enter. However, you can enter it through border gates (by car) if you have already obtained the visa. But I won't recommend it. Just get a flight. If you fly from Bangkok/Kuala Lumpur, Air Asia flights are pretty cheap. about 5 years ago