I fly into Saigon on Nov. 26, arriving 23:10. I am considering flying on, probably to Bangkok, w/in 24 hours. Is there a way to do this w/o incurring the cost/hassle of getting a Vietnamese visa? Can I simply hang out at the airport on the international side of immigration until a flight the next a.m.? Is there such a thing as a formal "transit visa." The VN embassy site is not so helpful on this.
If you come from a country that has a bilateral agreement with Vietnam, you can enter for up to 15 days without a visa. For all other nations, a visa is needed.
My understanding is that once leaving the plane, the sterile environment between the plane and the customs/immigration counter is not a place you can stay (for any length of time).
Legally, I understand that you are in 'no mans land' between the time you left one country and enter another. And, when you are actually in another country, the building area between the plane door and customs/immigration is a courtesy for the convenience of plane passengers. The alternative is that a nations' officials would enter the plane and do all the paperwork before you got off. In SaiGon, in the heat, passengers would love this (NOT).
Many years ago, I was at TanSonNhat airport in a plane and one person was not allowed to leave the plane as they did not have the necessary paperwork to enter VN. The airline company had to look after that person till the plane departed (I'd hate to think how hot it got inside the plane while it was reloaded, etc.). Today, such people are put in a lock-up awaiting deportation (been there, done that).
There are occasions when one does not need a visa, and they are when you are stopping over on a connecting flight. For example, Vietnam Air from (say) Phillipines to Bangkok via SaiGon. In these cases, you'll be ushered into the passenger waiting area (the area after a pax has gone through customs/immigration to leave).
If your intended onwards flight is not a connecting flight, or not with the same company, you'll have to check in. That means you'll have to enter the country of Vietnam, and then depart.
At SaiGon airport, there is a 3 day Transit Visa available. On this, go here to look, its called a C1 Transit Visa.
However, you MUST have your departing flight details to gain same, and the cost is about the same as a normal 30 day Tourist Visa.
Hope this helps.