We have a thinner winner in the world of tablets. Huawei's new MatePad Pro Max checks in at 4.7mm thick, making it the world's thinnest tablet. The bad news for US shoppers? You might not be able to buy it.The Chinese company launched the device on Thursday at its Now Is Your Spark product launch event in Bangkok, but it did not announce where it would be available. Fine print on the product web page reads, "Available only in certain countries or regions."A representative for Huawei did not immediately respond to a request for comment.The US government severely limits Huawei's ability to…