Best idea would be to stay a few days and a number of locations. Langkawi is nice and restful (try the 'island hopping trip'). You can see the whole island in a day. The aquarium at Pantai Cenang is good for an hour. Duty free shopping there and also at Kuah, the principal town. 90 minutes gets you over the mainland (Alor Setar or Kuala Perlis) by hydrofoil. The other cities and resorts mentioned are good choices, but also consider East coast resorts such as Kuantan or Kuala Terenganu, both on the South China Sea. If you go to Johor Bahru, you're just a few km from Singapore, but you need to do the full immigration gig to go there and back. Or to get away from the tropics, go up to Cameron Highlands, where the weather is like a summer's day in Kerry (circa 6,000 feet). They have tea plantations there. Or, for the 'Blackpool on a mountain experience' go up to the Genting highlands where they've got entertainment, gambling and amusement parks.