No, you do not. But please allow at least 3-4 hours time between the two flights (!) - this is very important. I transitted in DME, arriving on OS from VIE going to SIN on SQ: no visa is needed, as it's two international flights leaving from the same terminal. When you disembark the aircraft, you have to use Transaero's transfer desk to get your boarding pass to SIN ... they were *very* inefficient in my case: the lady took my passport and ticket and just went away for 1 1/2 hours ... I was panicking when she arrived *just* in time for the flight ... I rushed through security, found my gate and off I was ...