I am off to Bangkok on the 10th January to start backpacking on my own around Thailand, Laos, Cambodia and Vietnam for 4 months. Staying in hostels, is it easy to meet people? I always wanted to travel on my own but getting nervous now!
Any advice would be great!
SE Asia arguably has the greatest concentration of nervous first time backpackers on the planet.
Not only is it super easy to meet other travellers exactly like yourself, you'll actually have to be careful not to become so immersed into the backpacker scene that you never see or experience the actual culture of the places you're visiting. There are LOTS of backpackers in SE Asia (and everywhere else that has a firmly established Gringo Trail) who never breakout of the hostel scene, ever.
In other words, meeting other young foreigners like yourself is the last thing you have to worry about in SE Asia.
Relax, have fun.
As CT says, it's really easy, and I should know, as a rather shy guy myself.
You will find the Vietnamese to be extremely outgoing - use it to your advantage, but also be wary of those who would like to relieve you of some Dong!
Everyone in SE Asia is keen to practice their English, and an excellent way for you to interact with them. My advice is to get away from people you meet in your hostel, and meet the natives - maybe do a little volunteering, or just go ask them questions (they love it when you try out their language - quite difficult in Vietnam, but a little easier in Thai/Laos).
The more you read here and on Travelfish.org the better! Remember that Indochina is considerably less affluent than Thailand.
The people of South East Asia are very humble, kind and down to earth. You will have a great time meeting them. The people of South East Asia have a rich culture and history hence don't at all worry in going on a solo visit to South East Asia.