Haven’t really planned anything for Asia, just started looking at visa requirements for a bunch of countries such as Vietnam, Laos, Cambodia, India, Indonesia, Burma, and a few others. It looks like will need to plan ahead, rather than plan as I go.

As all of these countries require a visa prior to entry. Even if visa can be obtained on arrival, for example Vietnam will need a letter of permission to get visa on arrival. This visa option is only available if traveling by air, so making taking by bus or train impossible.

On top of that, the visa fees accepted are USD and local currency only. Definitely a lot more research is need while crossing borders.