I agree! I've been traveling solo since 2002 and it's my favorite way to travel. I take about 5 solo trips per year. As for Southeast Asia, I did Cambodia on my own and Thailand with 2 friends. I planned both itineraries.
I have moved away from booking tours with groups because I learned that I can do it myself (using a local tour guide) for far less money. For example, I booked my flight to Cambodia and then found a local tour company with good reviews on trip advisor. I booked a few day trips or 3/2s with that company. I booked all of my own stays. It was very cheap. For Thailand, I did the same. TripAdvisor makes it very easy.
This way, I get to meet interesting people and be part of a group when I want, yet I have the fun of sorting out when and how to get there - as well as being able to spend a day completely on my own when I want.
Many women don't think they can travel alone. It's simply not true. It's safe and very rewarding.