The Red Bull duo have looked fastest ever since they began practice on the Marina Bay circuit and team principal Christian Horner is upbeat about his team's chances this weekend.
Max Verstappen qualified in second place ahead of Red Bull teammate Daniel Ricciardo, with Kimi Raikkonen steering his Ferrari to fourth place ahead of Hamilton and his Mercedes teammate Valtteri Bottas.
"I don't know where Ferrari have picked up that pace", he added.
"But after a slightly messy Q1, track evolution saw times falling dramatically in Q2 and Q3 and neither Red Bull managed to catch Vettel".
"We will have a TAG Heuer Renault-provided engine and that will be the case for next year", Red Bull principal Christian Horner said on Friday after McLaren and Renault announced a new three-year partnership.
Red Bull Racing was expected to excel here, as the team did at the last low-speed circuit at the Hungarian Grand Prix, but surprising was that Ferrari, ordinarily very strong on street circuits in 2017, did not feature in the top eight. I think it's going to be very hard.
Bottas has exceeded expectations as Lewis Hamilton's teammate, winning two races and securing seven other podium finishes to emerge as an outside contender for the title.
Not only was the Mercedes drubbing a disappointing result for Vettel in front of Ferrari's passionate tifosi, but it also cost the German the overall championship lead he had held all year.
The infamous durian fruit, banned by many hotels and airlines in Southeast Asia due to its overpowering odour, nearly proved too much for two Red Bull drivers. It was a bit of a struggle to get there, but for now I am just happy we got the vehicle where it deserved to be and now we take it from there.
Valtteri Bottas has conceded Mercedes are "really struggling" in Singapore and have a mountain to climb if they are to get on at least one auto in a podium spot.
His impressive streak at the night race includes three straight wins from 2011-13 during his run of four straight F1 titles with former team Red Bull.
Hamilton has been on pole position at both races since the summer break, and qualifying is crucial in Singapore with overtaking virtually impossible.
"We were quickest in every session apart from the one that counts", he said. I got everything I could out of the auto, I gave it everything and more, literally threw the sink at it.
The second McLaren-Honda of Stoffel Vandoorne was ninth, well ahead of 10th-placed Carlos Sainz Jr.