The three stars are just for the fact that I kept watching to the end and had no idea what would happen.
When I think of King Arthur and Excalibur I never think of Thailand, kick boxing, building-sized evil dolls a la Ghostbusters, space ships (space rocks?), alien technology or even extra holy grails that aren't the main holy grail. But this movie has them all.
It is a terrible, low budget, badly overacted movie but who could predict any of the weirdness they added to a King Arthur story!
I say watch it (only if it's free) just for a laugh ... or to be stunned into silence.