JM,
You are going to need a multiple entry visa or buy two 30 day visas. I think it really depends on where you
are going to enter VN. If you are flying into VN, I would use one of the 'visa on arrival' services. I talk about
my experience using the 'visa on arrival' in my blog, "Off to SaiGon". This will cost you $85: $35 for their services, $50 stamp fee paid at the airport to VN Immigration officials. This is probably your cheapest option.
If you are arriving via land border, you can buy a 30 day, single entry VN visa in Phnom Penh for $30. Other
countries charge more than this for a 30 day VN visa. It will depend on where you buy your VN visa to see
what option is best for you. Send me a PM if you have questions.
[ Edit: Edited on 12-Feb-2009, at 00:25 by vegasmike6 ]