The prime minister of Thailand is the head of government of Thailand. The prime minister is also the chair of the Cabinet of Thailand. The post has existed since the Revolution of 1932, when the country became a constitutional monarchy. Prior to the 2014 coup d'état, the prime minister was nominated by a vote in the Thai House of Representatives by a simple majority, and is then appointed and sworn in by the king of Thailand. The house's selection is usually based on the fact that either the prime minister is the leader of the largest political party in the lower house or the leader of the largest coalition of parties. In accordance with the 2017 Constitution, the Prime Minister can hold the office for no longer than eight years, consecutively or not. The post of Prime Minister is currently held by Pheu Thai Party politician and former CEO of Sansiri, Srettha Thavisin.

A prime minister or chief of cabinet is the head of the cabinet and the leader of the ministers in the executive branch of government, often in a parliamentary or semi-presidential system. Under those systems a prime minister is not the head of state, but rather the head of government, serving as the principal administrator under either a monarch in a monarchy or a president in a republican form of government.