Searching for "Thale Waek" shows a walkable sand bar.

I see it in stock photos: 
https://www.shutterstock.com/search/thale-waek-krabi
https://cdn.prod.rexby.com/image/b05458f602814330bb34b4486c108fa2

And recent social media pics:
https://www.instagram.com/explore/search/keyword/?q=%23thalewaek
https://instagram.com/p/DRCngnsio_f

I suspect it's tidal.