Olympic medallist Saina Nehwal and B Sai Praneeth advanced to the semi-finals of the Thailand Grand Prix Gold badminton tournament with convincing victories in Bangkok today.The second seeded Saina, ranked 11 in the world, defeated Japan's Haruko Suzuki 21-15 ,20-22, 21-11 to make the last-four stage following the women's singles clash that lasted one hour and nine minutes.The 27-year-old London Olympics medallist, will face Busanan Ongbamrungphan in the semi-final.Earlier, the third seeded Praneeth comfortably defeated Thailand's Kantaphon Wangcharoen 21-16 21-17 in the men's singles section at the Nimibutr Stadium. The world number 24 took 50 minutes to complete the task against his opponent, ranked 102 in the world.