I have something of a soft spot for Khanom, at the extreme northern end of Nakorn Si Thammarat province. I spent many pleasant long weekends there several years ago, when I had friends in the area.
It's not that the beaches at Khanom are that great. They can't really compare to the white sand and calm waters of Samui just a few kilometers to the north. Khanom's beaches are a bit wild by comparison. They're a bit rocky and windswept. But that, along with the solitude found there, was in fact the attraction.
In the mid-1990s, there were no more than a half dozen groups of bungalows in operation on the beach. There were no high-rise hotels and hardly anybody even knew about the place.
That has since changed. There are at least a few low rise hotels on the long stretch of beach. However, Khanom remains far off the international tourist trail, so if you're looking for a bit of quiet it's probably still a good choice. Khanom is also very handy for exploring some nearby national parks, making the beach a good base for eco tours.