use this,, i use A6 pro for my game "Widy lost in wonderland"

sky cube
{
type=<sky_large_1+6.tga>;//u need that file
flags=cube,overlay,visible;
material=mat_sky;
layer=5;
}

and

action langit // atach action on your sky sphere model
{
while(1)
{
vec_set(my.x, camera.x);
my.pan += 0.1 * time;
wait(1);
}
}