As there is no real beach around the town Surat Thani, the nearest place for a day at the beach is in Khanom district in neighboring Nakhon Si Thammarat province. I went there three times already, as when staying in Thailand at least some time at the beach simply belongs to the itinerary. What I like at the beach in Khanom is that they are still quite unknown to foreign tourists, who all are found on Ko Samui - which also has great sandy beaches, but to me is way to crowded already.
Along the beach there are many small resorts which often include a restaurant, as for Thai tourists traveling usually means eating at a different location. Of course having fresh seafood directly at the beach is something I enjoy as well. The last two times we went to the Nai Pet beach (หาดในเปร์ต), this time we went a bit further south to Nai Plao beach (หาดในเพลา) and stayed at the only hotel of the whole area, the Supar (sic!) Royal Beach Hotel. Nai Plao beach is much shorter than the the Nai Phet, the two are separated by a small group of rocks which make a really beautiful view.
The beach is reasonably clean, inevitably there is some garbage left by careless people but most of the non-natural stuff washed ashore is styrofoam torn off from the fishing nets. But to be honest I had to look a bit to find that long stretch of garbage in the photo. The sand is fine, some shells can be found as well, though most are already broken. Last time I also saw several eremite crabs walking on the beach, the one I successfully photographed however was already dead as that one did not run away from my camera before I could focus it well.