(Could be late for the OP, but...)
I haven´t heard of anyone, who had shipped a foreign-registered bike into China or Vietnam, and succeeded in clearing the customs (and I mean regular tourists, not counting the people who live/work in those countries, that´s when it might be different).
You say you´ve already tried land borders to Vietnam, and it didn´t work. Maybe that´ll give you some idea, how it will be, if you try to ship it in? Much more probable, that you´d get lucky at a land border.
Strangely, both of those countries seem actually possible, but the flipside of the coin is: you´ll pay big time, and you can´t just pop up at the border, it´ll have to be arranged long in advance. Not a realistic option for everyone.
India is possible with a Carnet, but shipping in could be a bureaucratic nightmare* (I´ve only shipped out from there, and that was hard work!)... but that is a country, that you can do - legally, and without paying a small fortune! And me, I wouldn´t try my luck with a faked carnet, but its up to you to decide, what you want to do.
* edit. May be easier to ship to Nepal from SE Asia, and many travellers seem to do just that.
Last edited by pecha72; 30 Dec 2010 at 17:10.