It depends on your style. Some like to shoot ultra wide such as fish eye and 20mm. Some like to shoot at 28, 35mm. All I can suggest is to carry a lens which you are most likely to use. You don't need a fast F2.8 lens for landscape cos you are shooting mostly F16, F22 anyway! Its more useful that you carry a light lens to reduce encumbrance and a zoom, cos when you are shooting on top of a mountain, its not easy to move forward or backward several hundred meters to get that crop or magnification you want. Its not like street photography where usually many, including myself will use a prime and fast lens. Don't forget, when doing landscape, you are already carrying loads of stuff, such as tripod and your hiking gear.
During my backpack trip to India and Scotland, I carried 17-35mm and 50mm F1.4 lens. It covered all my needs. I shoot mainly landscape and street photography.
How do you know which lens you'll like or use before even going for the trip? Treat Singapore like the place you are going to. Go around and shoot and see which lens you end up using most of the time to shoot the type of pictures you are likely to shoot when you are there. Don't end up carrying whole load of equipment which you find superfluous, but worse still, take away the joy of the trip! You are going there to have fun and soak in the sights, not to be a mule and cracking your brains trying to change from 1 lens to another.