In The Blue Lotus, Tintin talks to Chang about various 'silly' stereotypes held by Westerners.
The story is pretty thoughtful in its representation of Asians.
But in earlier adventures, Herge drew his Asians very differently, like here in Tintin in the Land of the Soviets:
And the original B&W version of Tintin in America has a scene where Snowy is afraid he'll be eaten by some Asian clouts. I've seen that frame once and can find numerous references to it online, but I cannot for the life of me find an image of it online. But either way, Hergé himself once subscribed to those stereotypical notions that he ridicules in a later book.