Bus from Bangkok to Ho Chi Minh City

There are no direct overland options of any kind between Bangkok and Ho Chi Minh City, it is a journey that will take a minimum of 2 days and most travellers would seek to break the journey at least once if not several times (consider Siem Reap for Ankor Watt, Phnom Penh and Sihanoukville.) If you do want to travel through breaking only once at Phnom Peng then follow the detailed advice on this site on travelling between Bangkok and Phnom Penh. From Phnom Penh to Ho Chi Minh City there are bus services run by a number of different providers. The journey time from Phnom Penh to HCMC is around 7 hours and the fare around $12-14.