This is a scene from the 1955 Disney movie Lady and the Tramp. Its inherent racism has been discussed elsewhere I’ll just add that the cats actually have buck teeth, a common feature of asian caricatures especially around the time of World War II, only 10 years in the past. Siam is actually a region of Bangkok, Thailand, but Thailand supported Japan in the war, so fair game I guess.
The song itself was voiced and co-written by Peggy Lee, a singer and actress of the day. You can watch a pretty camp video of them recreating the creative process on Youtube. Here we’ve fast forwarded to the best part.