Originally Answered: What should I bring for a 3-day travel to another country?
Wow, sounds like a great trip!
First of all check the weather reports for where you'll be going (www.weather.com or similar). If it's very humid then you're probably not going to be comfortable wearing jeans more then one day, especially if temperatures are high. I'd take 3 pairs of jeans or shorts, 3 t-shirts, 1 light sweater and a light raincoat. As for shoes: if you're going to be doing a lot of walking then hiking boots or Teva style sandals would probably be best. Otherwise just wear what you usually would. I've never taken slippers when travelling, never needed them either.
I wouldn't bother bringing water, it'll weigh down your luggage and you're going to be able to get water there.
Most hotels supply single-serving size shampoo and shower gel or soap (if not in the room then you can ask at reception) but if you'd rather use your own then by all means bring them. If you're only going for 3 days then best to bring half-empty bottles: you won't need any more, you're not carrying the full weight, and the last day you can chuck them leaving you more room for souvenirs :-)
I personally don't like inflatable pillows
, you can just bring your sweater along in the bus, and use that for a pillow.
If you're worried about pickpockets then you can get one of those strap-around packs that you can keep your money and passport in. If you're keeping valuables in a backpack then you can wear it in front of you in busy areas to prevent pickpockets going through it without you noticing it. And take a photocopy of important stuff (flight information, passport,...) and keep that in your luggage. If your papers were to get stolen then that'll save you some hassle.
If you're taking a waterproof jacket then I wouldn't bother bringing an umbrella. You can ask the hotel reception to give you a wake-up call if there's no alarm clock in the hotel room. If you're bringing a cell phone then that probably has an alarm clock function too. Check in advance that your cell phone will work in malaysia: roaming has to be activated (check with your provider) and your phone has to support 900 and 1800 MHz frequencies (check on the manufacturers site).
Oh, and don't forget to bring a camera, and to have a great time :-)