Science and me have a tenuous relationship. The relationship between the Earth, the Moon and the water bodies of Earth mostly illudes me. Nevertheless, there is a question about when and how much when looking at the tidal movements. I have found 2 websites displaying the tides in Koh Phangan. The one I like best is http://phangantide.info/. You can find out when the low and high tides are going to happen as well as the depth. It seems that today high tide is at 15.03. At this point something is going to be 44% and something else is 1.8 metres.
If you are in Srithanu or one of the other west coast beaches then this website might be useful for you. If you are staying on the east coast than the state of the tide is purely academic as anytime (outside of storms) is a good time for a dip.
When I went down to Srithanu beach to take these photos there was a group of lads playing football. They would be interested for future games perhaps when the next low tide was due, which seems to be much of the time in Srithanu.
In the pictures below you can see Srithanu beach in all its low-tide glory. Acres of sand. In the distance you can just make out Ang Thong Marine Park.
It isn’t exactly the beach you see on travel brochures and hotel websites, but, nevertheless, it is beautiful. The expanse of space, the domination of nature; and in this circumstance it really is unspoiled.