I have visited Yin Thai various times now and while I overall like the place, I feel that the quality of the massage depends on a lot on who treats you. I always feel better afterwards, but I find that my requests aren't always listened to (for instance, I tend to have problems with my upperback and neck, but when I mentioned this the majority of the massage focussed on my legs).
The massages at Ying Thai are really strong and great for relieving tension. They are also great value - I have been several times and will be going back. I would recommend!