Entering Vietnam with your vehicle is sadly as big a problem as China is. With one exception: China you can officially do, if you got the budget, time and patience, but Vietnam you cannot. Not even with any "under 175cc bike" (there is no such rule anymore, if there ever was one, which I must say I doubt).
You may try, but you´re most likely rejected at the border. If you have only 1 bike, you might be able to sneak in, but no-one can guarantee that. Or if that way will get you into trouble later on in Vietnam.
Bangkok and Kuala Lumpur are the best places for shipping in that area.