One of them has to be dropped!!!

HI All,

right im planning my year out and due to various reasons i need to cut some days out of my trip and ive isolated it down to asia.

my first plan was to fly in to Vietnam, Hanoi and then overland, somehow, to Ho Chin Mi - then overland into Cambodia - then overland into Laos - then overland into Thailand down to bangcok.

I needed to cut out some days so i have taken out cambodia, however upon mentioning this to some friends they have all said no dont, and i should drop Laos.

In all honestly i dont know a whole lot about the areas, but i know i am going alone so would like to be in the places where there are the most single travellers and where the better partys are, hence why i kept laos in as im told that is pretty good.

Im arriving in vietnam 8th November this year, and have switched my flight into ho chin and plan on working my way up to hanoi and then into cambodia. All 3 countries (vietnam, laos, thai) are to be done over a period of 42 days....racy i know!!

So i suppose my questions are

1) where are the best countries for single travellers, easy going and easy to hook up with
2) where is the best place/friendliest for party/drinking culture
3) is it possible to overland or am i being nieve thinking getting on trains/buses up and down these countries is possible
4) realisitcly is 42 days doable ?

Thanks so much for any help

James :)