They're definitely Tonkinese.
This particular breed of cat is a natural breed in Thailand but it is actually a cross between Siamese and Burmese. It is possible that the very first Burmese were infact Tonks as Burmese breed true but Tonks don't due to the varying degrees of the expression of the colour restriction gene.
Breeders will obtain Tonkinese by either mating Burmese to Siamese or now more usually, Tonkinese to Tonkinese. However, the former mating will return a whole litter of Tonks, but the latter mating will return a ratio of one siamese kitten, one burmese kitten and two tonkinese kittens.
Those aquamarine eyes are very characteristic to the Tonkinese breed.
