Commonly asked questions for a Vein Doctor, Dr. H. Ray Rassai. Dr. Ray Rassai is a highly distinguished vein doctor and also a founding member of the BASS Vein Center located in Walnut Creek.Dr. Rassai practices general surgery with a special interest in minimally-invasive hernia procedures, gallbladder issues, thyroid, and parathyroid disease, colon cancer, and varicose veins.