This research was conducted to study the effect of fermentation on the physicochemical, rheological properties, and bioactive compounds of Chai Nat (CHI) and Mali Nil Surin (SU) rice flour and the effect of fermented Mali Nil rice flour substitution on rice noodle qualities. Production of fermented rice flour was modified from the traditional method by using a tray dryer to control fermentation temperature at 40°C. Fermented rice noodles were produced by substitution of fermented Chai Nat flour (FCHI) with fermented Mali Nil Surin flour (FSU) at the level of 0, 10, 20, and 30%. The results indicated that moisture, protein content, and pH value of fermented Chai Nat and Mali Nil Surin rice flours decreased after fermentation, while the amount of amylose and total starch content increased (p<0.05). An increase in lightness (L*) and redness (a*) and decrease in yellowness (b*) values were observed after rice fermentation. The setback value of FSU flour was lower than SU flour and this value was higher in FCHI flour compared to CHI flour. Substitution of FSU flour to FCHI flour at 10 to 30% showed a significant decrease in pH values of rice noodles. The lightness (L*) values, hardness, and adhesiveness of rice noodles decreased, while a* and b* values increased with increasing levels of FSU flour replacement. High level of FSU flour substitution decreased storage (Gʹ) and loss modulus (Gʹʹ) of rice noodle paste. Storage modulus (Gʹ) was higher than loss modulus (Gʹʹ) over the tested frequency, indicating elastic properties of rice noodle pastes. All sample exhibited tan δ (loss tangent) lower than 1 indicated an elastic component that a solid-like. Partial substitution of FCHI flour with FSU flour tended to increase the antioxidants and total phenolic content of rice noodles.