As with everything Star Wars, this answer comes to you in two parts:
No, it is possible for Naboo to be ruled by a male; at least one King of Naboo has been identified in canon sources:
King Veruna is revealed in the updated Star Wars: Complete Locations DK reference book to have added a library to the Theed Royal Palace:
The previous ruler, King Veruna, established a vast royal library collection in this tower during his 13-year reign
This image also reveals (in the blue circle) that a previous King had a cousin who established a banquet hall in the city:
Banqueting rotunda built by the Earl of Vis, a cousin of the old king
It's possible this is also a reference to Veruna, although we can't be certain
Finally, in a flashback scene in the canon novel Tarkin, then-Senator Palpatine mentions a King of Naboo (emphasis mine):
In the Seswenna sector, several lommite mining concerns are vying for the attention of the Trade Federation, which is determined to forge a monopoly in the free trade zones. Even on my own Naboo, the king finds himself embroiled with the Trade Federation and off world bankers with regard to our plasma exports.
Tarkin Chapter 9: "As Above, So Below"
This scene takes place twenty years before the main events of the novel, which itself is set five years after the end of Revenge of the Sith, meaning this exchange occurs two years before the events of The Phantom Menace; the King Palpatine refers to is almost certainly Veruna, but we can't be totally certain of that.
There have been several Kings of Naboo, though far fewer of them than the Queens:
- Narmlé, who was mentioned in the now-defunct MMO game Star Wars: Galaxies
- Jafan, who gets mentioned in a few of the Star Wars background books
- Bon Tapalo, who appears in the novel Darth Plagueis
- Ars Veruna, Padmé's predecessor, who appears in a couple of books and comic books