The OP's question has nothing to do with Thailand. It could arguably go in the New York forum.

In addition to asking your original airline if they can transfer your bags all the way through (which is certainly permissible; the only customs issue that would require you to re-check them is on the return back into the U.S.), try to get your boarding pass for your onward flight in advance as well, so that you don't have to wait in the check-in line at Terminal 7. You didn't say which airline you are traveling (ANA? Cathy Pacific?), but see if they allow you to check in on-line and print your own boarding pass. Most international carriers don't, but they might.