For "quality certificate", as you know, it's a document issued after inspection. However, according to China law, tyre exporting do not need commodity inspection like before from Aug 2013, so China's Commodity Inspection&Quarantine can't issue this certificate any more. I mentioned this issue in the email sent you on 24th and 29th Oct.
We've double check with another Thailand customer, you can use a "certificate" as attached to do custom clearance. With this you can clearing your goods fluently. Pls check with your custom.