Can I travel from Thailand to Vietnam without enter Cambodia?

Is $500 enough for a one week backpack travel to Vietnam-Laos-Cambodia-Thailand…

• My best friend and I are planning a December trip to backpack through Vietnam, Laos, Cambodia, and Thailand. Is $500 enough as pocket money? Would 1 week be enough for us to visit the hot spots of all 4 countries? Is there a train that travels through all these countries and how much would it cost us? How much should we set aside for lodging? Do you have any suggested itineraries? I'm from the Philippines and the only points of entry that I know are: Bangkok, Thailand and Ho Chi Minh City, Vietnam. Your help would be very much appreciated :)

• Answer:

  One week is too short a time to cover four countries but $500 will definitely be enough if you only travel by using the night buses and save on lodging.This will be city hopping. 1) arrive Bangkok,city tour then evening go Mochit Bus terminal/or Hualampong train station night travel to NongKhai for morning crossing to Vientiane(Laos) 2)Vientiane city tour then the night bus to Vinh(Vietnam) 3)From Vinh take a day bus down to Ho Chi Minh.Find budget hotel and sleep. 4)Ho Chi Minh day tour.Afternoon get bus to Phnom Penh(sleep) 5)Phnom Penh to Siem Reap. 6) Siem Reap arrange bus to Bangkok. 7)Fly home. Do enjoy yourselves and by the way December is a cold and wet season