Can I eat chicken that was cooked, frozen, and thawed in the microwave yesterday?
I certainly wouldn't risk it. The conventional wisdom with things like frozen cooked foods is to eat them within 24 hours of defrosting. If you defrosted it in the fridge you might have a little leeway (but it would still be a risk) but as you defrosted and reheated it in the microwave the likelihood is that eating will make you ill.

Definitely don't reheat it again, you should only ever reheat things once (though I'm less certain of this as many recipes call for cooking and reheating things a number I'd times) as the various heating and coolings increases the risk of dangerous bacteria growth.