The benefits of Thai massage are cumulative. It might have taken days, weeks or even years for you to develop your back pain or stiff neck, so it is impossible for one Thai massage to reverse these conditions. Successive Thai massages build on the good effects of your first Thai massage, as long as you don't space your Thai massages too far apart. If you wait too long between treatments, then each Thai massage will start you back at square one.
Here are some suggestions for how often to schedule a Thai massage.