wondering if there are any resorts in Patong, large or small that permit non-guests to make use of their pool facilities for a reasonable fee..

I have used the Novotel at Kalim from time to time and found it ok. Various membership packages for pools and small gym - perhaps a little on the pricey side if I remember correctly - but facilities ok (towels, hot shower, lockers, sauna etc) and sunset coincides with Happy Hour at the bar, which is nice. In high season you need to experiment with your timings if you want to swim lengths and avoid the tourists but low season normally ok.

You're welcome.

Expat hotel i go there eat drink and swim nice spot

From the thread title I thought the Op missed that big body of water on the other side of the beach!!