Code:

---

 
function mtl_vegetation_init
{
 vec_set(mtl.emissive_blue,mat_model.emissive_blue);
 vec_set(mtl.ambient_blue,mat_model.ambient_blue);
 vec_set(mtl.diffuse_blue,mat_model.diffuse_blue);
 vec_set(mtl.specular_blue,mat_model.specular_blue);
 mtl.power=mat_model.power;
 mtl.albedo=mat_model.albedo;
 //mtl.skill1=pixel_for_vec(vector(188,0,0),0,8888); // the first value in the vector is the threshold
 mtl.skill1=pixel_for_vec(vector(40,0,0),0,8888); // the first value in the vector is the threshold
}

material mtl_vegetation
{
 event=mtl_vegetation_init;
 effect=
 "
 texture entSkin1;
 dword mtlSkill1;
 technique vegetation
 {
  pass p0
  {
   Texture[0]=<entSkin1>;
   ZWriteEnable=true;
   Zenable = true;
   AlphaBlendEnable=false;
   AlphaTestEnable=True;
   AlphaRef=<mtlSkill1>;
   AlphaFunc=Greater;

   CullMode=CCW; // CCW or None
 
   ColorArg1[0]=Texture;
   ColorOp[0]=Modulate2x;
   ColorArg2[0]=Diffuse;
  }
 }
 technique fallback{pass p0{}}
 ";
} 

---

my.material = mtl_vegetation;

This will solve your sorting problems. If you want alpha blending change - AlphaBlendEnable = True;