This is a Buddha Head from what I believe could be Khmer (having looked at other similar photos online, the style of carving and head shape fits). I can’t be certain but it appears to be made of sandstone/clay. The top of the crown is removable (see photos) dimensions are 54cm height and 31cm width approximately

It was bought in Northern Thailand around ten years ago and then donated to a UK charity Imagine Project to benefit Tibetan children.