I personally will not re-offer a thawed rat that is more than 5 hours old (since starting the thaw process).

Just offer it at night, if he doesn't take it, leave it in the enclosure with him. If it is still there in the morning, throw it away.

Don't offer him food and then offer again a few hours later if he refuses, if he refused, he refused. Try again next week. Offering over and over again in small intervals will make the snake less likely to eat. You are more likely to get him to eat if you wait a full week before offering again.