Can I make this with frozen chicken in an instant pot or does the chicken need to be thawed first?

Sounds like a yummy recipe! With the recipe calling for boneless, skinless thighs, you may be able to start with frozen chicken. If the thighs are not individually quick frozen, I would try defrosting in a microwave long enough to separate the pieces. And of course, lengthen the cooking time and use an instant read thermometer to make sure the thighs register at least 165 degrees before serving. Unlike breast meat, thighs are pretty forgiving if you overcook.