You're clearly a foreigner, since you've confused it a little. KHL is just some fraud nutjob claiming the non-existant throne, since Hungary isn't a kingdom since the times of Horty's reign. Also, diplomatic relations between Hungary and Croatia are pretty strained in the last few years. They're argueing over some joint economic treaty or project of theirs... I doubt it will materialise. That river cargo ship project on the Danube still hasn't materialised - ever since the 1970s, when it was first proposed...
The Treaty of Kiev, 1933, which absolved the border dispute of Hungary and Croatia, technically created a supra-national entity called the "Kingdom of Hungary-Croatia," at Hungarian insistence. However, both states have since declared themselves "republics within the Union." KHL wants Slovakia to become a signatory to the Kiev Treaty.
Of course, the President is a figurehead position, selected by the old Hungarian nobles in Slovakia, if I understand it, but it still seems an interesting development.
(OOC: How about this TL for Slovakia/related. After WWI, racial and political tensions within the Austro-Hungarian Empire ]are even greater than OTL, causing Slovakia to fragment into minature republics, communes, and fiefdoms ruled by the old nobility and Czech irredentism to go out of control [yet strangely not directed at their Slovakian kin]. In 1990, Slovakia is reunified. Part of the (myriad) conditions for the reunification of Slovakia is the nobles keeping their titles, and electing the President from among themselves. The President has no powers except for granting pardons. Of course, that's not the only condition, the Bratislavan Supreme Soviet was legitimized and given the right to elect the Premier, who has no powers except to veto the president's pardons and appoint ambassadors. Real power resides with the parliament, which due to various reunification compromises consists of over 2000 members from over 600 political parties. Reunified Slovakia is not a very stable state (as nothing "reunified" ever is). It is in essentially a similar economic condition vis a vis the West because of 60 years of economic blocades from the Soviet bloc and between the Slovakian microstates. Also the, Soviet Union is much more of a force, since it, thwarted in its attempts to gain a "buffer" in Eastern Europe, is also spared the cost of rebuilding those states after WWII and subsidizing their economies. Instead it turns to Asia, and, critically, POD2 is that they are much more focused on the Middle East, meaning they are much more aggressive even than IRL in the Suez Crisis, and, crucially, manage to gain economic and military hegemony throughout the Middle East. As a result, Pan-Arab Socialism is much more popular, hence Greater Arabia. Igor Sikorsky never leaves Russia, hence Soviet helicopter divisions. It must be miserable having no gas over there. It's -10 degrees Celsius up here, and I can't imagine having no heating. I shouldn't take it for granted, our heating oil comes from Venezuela!)