The story of Yen Ta Fo. Yen Ta Fo is another Thai favorite noodle soup, which is very popular among Thai locals. The key character of this noodle dish is the reddish soup, which comes from Yen Ta Fo sauce. The red color is from a type of fermented tofu, which is the key ingredient of this sauce. Along with the fermented tofu, Thai Aree selects the finest quality of yellow chili, garlic, fish sauce and sugar to create our ready-to-cook sauce.