Koh Lipe is close enough to Langkawi that you can see it, all the way southwest in Thailand, so going there from Koh Phanang is not difficult, but it would require a whole day of travelling.
I heard a lot of people raving about Ko Tao, and it's super close to Koh Phanang, so would've been my choice if you've already planned on visiting Koh Phanang. Full moon party?
Langkawi was okay, it involved three weeks of heavy drinking. If you've been in SEA before then you might have noticed some beaches have tiny jellyfish (what I was told) that stings you, the main beach on Langkawi also had this, made the swimming annoying. They had some killer roti there though, we ate there almost every night, and an old lady selling homemade treats on the sidewalk had (amongst many other things) swetpotato noisettes, freshly squeezed watermelon juice and baked bananas.
On a whole it is kind of a boring place, if you want to meet some people, relax and eat some good food then I'd go, but Thailand is better, simple as.
