The idea is to break up adhesions within muscles and ligaments around the hips, etc. (in my case) which restrict the proper movement of muscles that are damaged areas that have gotten tight and painful. (Eventually this will help undo pain around the tailbone, I hope, but you have to start from the outside in.)
To do this, I lie on my side. The therapist (a chiropractor in this case) puts a lotion on her hands, presses deeply into certain muscles at the bottom of the thigh along the side, and slowly slides her thumb upwards while I slowly move my leg outward (sort of opening the "path" for her as she goes.) Does that make sense? As she slides her thumb upward through the muscles, we can both feel the tight spots because they are very sore or feel like pinches. I think this must be where the adhesions are. She will go up a specific muscle 3 times (more than that she says will cause bruising). She does this in various sets of muscles in the problem areas. At first you go one or two times a week, and then she stretches out the time between to two weeks, etc. She also does basic chiropractic adjustments and muscle testing to see if any muscles have "pooped out" from compensation and overuse.
She also gave me some piriformis stretching exercises, and I actually noticed more improvement from those, I think, than the other - but perhaps they worked well together.
The Thai massage works similarly to acupuncture (pressure instead) along muscles, and also includes having the therapist stretch your muscles for you while you are more or less limp (you don't do the work.) A few yoga stretches are incorporated for you to do at home. So it's kind of a mix of things, but it's all aimed at stretching muscles and breaking up adhesions that result from trauma or compensating for painful motions (like sitting).