I have been to Sansuk many times and it never fails. My therapist, Mam, was superb. She is extremely experienced and knows what she is doing.
My only suggestion is to have slightly thicker towels on the bed and the hole into which you place your head when lying face down. It's not at all uncomfortable, far from it, but maybe a towelling cover for your face would be better. Overall though, 5 stars!