In my opinion, the lounges in KL are a bit Meh. The Malaysian lounges are probably your best bet - flying to Phuket you should get away with using the regional one in the main terminal (A) rather than the ones in the (C) satellite (which aren't as nice, I don't think). And at least you avoid the horrors of the domestic lounge...
The A lounge has just been closed for refurbishment for 3 months, but should now be open again...