Q. What can I so to increase my Yorkies appetite. He seems to thin
A. What you can do is mix in some wet food, or some higher value food. If you are feeding him kibble, that can sometimes be boring! Imagine if your mother only fed you kibble day in and out.. wouldn't you be so sick of it? It's boring as heck! Try adding something amazing to it. Just make sure the thing you are adding is wet enough, and mushy enough to incorporate the kibble.. if you put, say, white meat chicken-bits into your dog's kibble, he could potentially eat AROUND the kibble, and only eat the chicken! If you use Freshpet http://freshpet.com/our-foods/our-brands/#/brand/vital-vital tubes of meat, or the wet food, you can mush that around into your pups food and that will get him more interested in eating it, I promise!
Lastly, I'd like to say that just because your dog is thin does not mean he is unhealthy. He could be perfectly fine! If he is full and doesn't want to eat, don't force it too much!