There are usually quite a few people on the Ban Tai Beach in December, in June and May and in November and October.
The air temperature at Ban Tai Beach allows sunbathing all year round. There may be some who find the water at Ban Tai Beach too warm.
From April to December Ban Tai Beach has rainy season. This is something to keep in mind when planning your trip since it is quite possible that you may be unable to sunbathe.