Ask HN: Possible to legally form a startup as a digital nomad?

I'm a developer, US citizen, out of college, and out of the country. With no desire to work for the man, and a strong desire to travel the world, my wife and I are living abroad. She's teaching, I'm doing freelance design and development work, while also spending a significant amount of time on a startup.

We have no plans to return the the US in the foreseeable future. We have no address in the US. We will also be moving from our current location (Vietnam) to another shortly. So my question is:

Is it impossible to legally register this startup?

As far as I know, I need to register my business name, register as an LLC, register with the tax board...but much of this has to be done in person.

My last US address was in California. Contacting the California Governor’s Office of Business and Economic Development was no help.

Is it impossible?