The broad bay of Bang Saphan Yai is probably one of the more low-key beach destinations in Thailand. Regular visitors here relish the fact that it's a footnote in most guidebooks, and dread the day the tourist community at large gets wind of it. We kind of agree.
Bang Saphan Yai is a small town some 80 kilometres south of the provincial capital Prachuap Khiri Khan and 100 kilometres north of Chumphon. It has a decent stretch of beach, a waterfall, red cliffs and a cave temple worth visiting. It's also the jumping off point for visits to Ko Thalu, which has reasonable snorkelling and diving.
Bang Saphan is a seasonal destination and in off-season, some places close-up or run with a skeleton staff -- on a really quiet day it can feel like you're the only person on the entire beach. For some people, this is perfect, but others may find it almost too quiet -- especially in low season -- as you're fairly isolated from town. This is not a party zone.
The beach has a steeper drop off than Ban Krut to the north, so it does make for better swimming, but overall, we'd have to say Ban Krut's beach is nicer than here. Much of Bang Saphan has an active fishing boat industry and small fishing villages are dotted along the way; because of this there seems to be a bit more flotsam on the beach, especially to the north where the beach really isn't very nice at all.
Bang Saphan is actually two separate towns: Bang Saphan Yai is at the northern end of the bay and Bang Saphan Noi is about 15 kilometres or so to the south. Most resorts lie near the beach some halfway between the two towns off route 3374, and while there is accommodation on the northern stretch, we don't suggest staying there on account of beach being quite poor.