no flight bookings required for bangkok (or embassy letter) If your visa office is immigration division 1 they are most simple and easy but if your immigration office is it square make sure to print off your hotel booking + if you have appointment you must print it out too. (along with everything else standard)
Just a heads up, thailand embassy in china ( atleast beijing) will typically call first for a quick over the phone interview before issuing visa. You may have missed a phone call.