I'll start my travelling through Asia soon, and regarding Vietnam, Cambodia and Thailand I confess I'm a bit lost on which direction to take.
First, I'm travelling alone. Then, some people say joining a tour is better and safer,like those all included tours, like the ones in gadventures.com, others say I can easily move around in these 3 countries by myself, no need to book anything in advance.
For those out there that have travel in these countries, let me know your experience, and what you think is the best option.
Also, about vaccinations, is it really necessary? or better to just take medication with me?
Very easy on your own. I wouldn't waste money on a tour. It is really easy to get around from town to town, find accommodation, restaurants etc.. with the help of a good guidebook, advice from fellow travelers, and assistance from hotel staff and travel agents locally. My guess is that anyone who has recommended an all inclusive tour has either never actually been there, or really has no sense of adventure.
However, many solo travelers do prefer to have a group of people simply to have friends to meet and share the experience with. I will assure you though, you will meet tons of other travelers on the road and you will rarely be alone. Try to stay in popular hostels and guest houses where you meet others. Also, you will find many opportunities to take short (1-3 day) tours around the region that you can book cheaply and locally and will be full of other travelers looking to make friends. For example - floating market visit in Bangkok; Mekong Delta tour; Halong Bay boat cruise; or village hike in North Thailand or Vietnam; or short guided tours of a historical site. These tours are great ways to meet others, and have a couple days of no planning.
For vaccinations - yes you need them. Go to a travel clinic and they will tell you what you need.