No, the King of Ireland did not fight beside William Wallace.
William Wallace was a prominent figure in the Scottish Wars of Independence against England in the late 13th century. He is best known for his role in leading the Scots in their struggle for freedom during a time when England sought to dominate Scotland.
At that time, Ireland was experiencing its own political struggles, primarily involving conflicts with English dominion as well. While there may have been some Irish support for the Scottish cause, notably from those who were also resisting English forces, there is no historical evidence to suggest that the King of Ireland personally fought alongside Wallace.
In fact, the political landscape was quite complicated, and alliances were often formed based on individual interests rather than a unified front. Various Irish leaders had their own battles to fight, which did not directly involve Wallace’s campaign for Scotland.