Tonga

Tonga is a "semi-constitutional" monarchy with a unitary state structure and a parliamentary form of government. The monarch has significant role in government, akin to the head of state in a semi-presidential system.

Of the 30 members of its unicameral parliament, 17 are directly elected at least every four years. Voting is done in single-member constituencies via single-round, choose-one plurality voting, aka first-preference plurality (FPP) or first-past-the-post (FPTP). Nine members are elected by the nobles from among their own ranks, and the Prime Minister may appoint four members to serve as members of parliament.