Bad habits in our body mechanics will destroy us faster than anything I can think of. I recently took some photos of my work and caught myself getting lazy in a couple of poses. We have to remember that just because we know the stroke doesn't always mean that the contour is the same match on each person. We need to remember the details of our work, after all nothing is the same when your always learning, healing, moving toward perfection.
When first learning Thai Massage I think most people just try to remember all of the different steps. Once you are comfortable with the routine it is much easier to start listening to your own body while giving the massage. If I don't feel refreshed after giving a Thai Massage then I know either my mind or body was out of sync. I have done 8 60 minute massages at a family reunion before and felt tired but physically fine. I worked a Thai festival at Union Station in Washington DC with a friend, we worked for 7 hours with just a few short breaks. I think Thai is one of the best massages to give for the practitioner, in fact if I end up getting too many deep tissue clients that I can't talk on to the mat then my wife or a friend is going on the mat to help center me.
Work with others who can watch what you are doing and give feedback. It would be helpful if you can find someone with experience in Thai Massage, if not someone who understands the body and movement will be fine. A good yoga instructor would be good. I think you can find a few Yoga instructors willing to give up a little time for a free massage. If you can't find anyone then video taping yourself can work also as long as you know what you are looking for.
Following are a few postural considerations (body mechanics) I have found very important to myself. It may help you also. Use straight elbows and wrists when giving palm and thumb compressions. A bend in the elbows results in elbow stress, overworking the pecs and more... Compressions should be your body weight on straight arms. Be close enough to your client so you are not reaching out forward and overworking yourself. Although it is a must to be forward flexed toward your client, do your best to be erect as possible and drop your body weight (do not push). It may help to consciously give a slight retraction to your rhomboids (major) and slight engagement of of mid-lower traps, keeping shoulders down and neck in line (watch the chin is not over extended or tucked, give a lttle lift to the sternum. Most work should be done in some type of kneeling posture on your toes... don't be lazy and sit "indian style" and don't work on a massage table (if truly performing a Nuad Boran Thai massage). AND BREATHE...