Hello Handsome Riley! Welcome to PT as a "mom's pup!" You are just a sweet one and have found a great home for yourself!

He doesn't look overly thin to me. As someone else said, I'd just put the food down for 10-15 minutes morning and evening. Set the kitchen timer. To me, a dog jumping bouncing and playing around as these photos suggest he does, is not a weak, ill, underweight pup!

If his energy level is good, he drinks, pees and poops, then he is self monitoring his weight and is fine.

Now digging in mom's garden, that could be a tough challenge to address!