Traditional, Classic and Modern Siamese
I think this is quite a nice picture for showing the three types of Siamese cats. The original Siamese cat shape is the top one. The is the Traditional Siamese and it has the nickname, “Applehead Siamese” because of the apple shape head (i.e. rounded in comparison to the long Modern Siamese head shape).
The Modern Siamese is the bottom one and the backlash or change away from the slender (oriental body shape) is the middle Siamese cat that I would call a classic Siamese cat and which is now a new breed called the Thai cat and which is registered with TICA but not the other cat associations.