Ragdolls are longhaired cats, so he/she isn't a Ragdoll. And unless you bought the kitty from a respected breeder, he/she probably isn't purebred Siamese either. I would guess that the kitten is a seal pointed domestic shorthair ("domestic" is what we call cats with no particular breed background). Now, it is true that all pointed cats descend from the original Siamese, so I suppose it wouldn't be totally inaccurate to say "Siamese mix", but most likely any purebred Siamese ancestors were many generations back.
Very cute little pointed kitten. I agree with Willowy on likely heritage. Ragdoll ancestors would probably show as much fluffier / longer fur and more rounded build plus the face is a different shape. Siamese tend to be more chatty.