If you want to get away from it all (and don't mind a bit of wildlife in your room) I can recommend
http://www.japamalaresorts.com/Malay...an-Island.html. Fly there with Berjaya Air from the Old Kuala Lumpur airport (Subang), then you need to get a 10 minute boat ride from the airport to the hotel.
If you're feeling flush, for more luxury but still in the jungle, The Datai on Langkawi is good too.
A 5 day trip to either would just about be doable. (But that's coming from someone who went to Seattle for a weekend!)