tdziemia
it does say REGIS,
If we compare the letterforms to other coins of Vladislas (denars and ducats), there are differences , For example, I do not find this A which resembles a Greek pi, on his early undated denars with this mint mark. Nor the L with two vertical srokes is more characteristic of earlier times.

But also true is that this was a time when the letterforms were changing from Gothic to modern.
Yes its REGIS, I was seeing things when I saw KAIS hahaha… But yes, the style is very strange, shield, letters… I think its a contemporary forgerie…