Why are you going? If it is to experience the country and people, travel by bus and train. That means going through China for which you will need a visa. From HK to Shenzhen, where you walk across the border into China to the bus or train station.; you will need someone to assist you through the intricasies of finding the right ticket office, getting the right ticket and finding the right bus.It is a large complex in the throws of reconstruction. May I recommend the Sunrise International travel Co. on the 40th floor of the China Resourses Building on Harbour Road, Waichai, Hong Kong.www.chinavisa.com.hk I went there to get my China visa. Very good service. Take a bus or train to Kunming and spend a little time in Quangxi province, maybe visit Guilin, but watch for pichpockets - it's a tourist destination. Take the train from Kunming to Vietnam - Lao Cai - and from there another train to Hanoi. This last train takes about eight hours. Kunming to Lao Cai probably 10 to 12 hours. From HK to Kunming , doing it in stages, should take two to three days. Overnight sleeper buses are good in China but the toilets leave much to be desired. I tend to dose on Noroxin, without which you should not travel anyway, which puts your system on hold for the duration of the journey. I do not know what a doctor would say to this. The only alternative is to fly to Hanoi and travel by train or bus, though road travel will scare the soles of your shoes. Cost? Cheap. But I cannot be specific, but as an example, a 14 hour train journey last year cost me 160 yuan = NZ$27 = US$19. A sleeper would cost perhaps 1/3 again.Have fun.