Prime Minister of Thailand Rajanubhab took over this role. In fact, the office most considered the precursor of that of the prime minister was the ancient office of "Samuha Nayok" (สมุหนายก), which was run by an "Akkhra Maha Senabodi" (อัครมหาเสนาบดี) or "chief minister in charge of civilian affairs". The first Prime Minister of Siam was Phraya Manopakorn Nititada, a judge. The title of the office was changed from "Prime Minister "of Siam"" to "Prime Minister "of Thailand"" in 1945 and then permanently with the renaming of Siam to Thailand in 1949. For most of its existence the office has been occupied by Army leaders;
Prime minister-designate leader of the largest opposition party therefore could still become prime minister-designate perhaps several weeks after the general election. The term prime minister-elect is sometimes used as a synonym, but in most circumstances it is technically incorrect: a prime minister is usually appointed by the head of state, and not elected to office by the entire nation, as is the case with some presidential polls. However, it has nonetheless seen common use in the media. Terms such as incoming prime minister and prime minister-in-waiting are also sometimes used, although the latter term is also sometimes used prior to an election