From นายก (naa-yók, “chief; leader”) + รัฐมนตรี (rát-tà-mon-dtrii, “minister of state”); literally "chief minister of state" or "chief of ministers of state"; calque of English prime minister; coined by Yu Udomsin (อยู่ อุดมศิลป์) in 1932, also known by his noble title Phra Tham Nithet Thuai Han (พระธรรมนิเทศทวยหาญ), a member of the People's Party of Siam; officially used since 10 December 1932 when the first constitution of Siam was enacted; borrowed by Khmer as នាយករដ្ឋមន្ត្រី (niəyŭəkrŏətmŭəntrəy) and by Lao as ນາຍົກລັດຖະມົນຕີ (nā nyok lat tha mon tī), both in 1945.
| Orthographic | นายกรัฐมนตรี n ā y k r ạ ʈʰ m n t r ī | |
| Phonemic | นา-ยก-รัด-ถะ-มน-ตฺรี n ā – y k – r ạ ɗ – tʰ a – m n – t ̥ r ī | |
| Romanization | Paiboon | naa-yók-rát-tà-mon-dtrii |
| Royal Institute | na-yok-rat-tha-mon-tri | |
| (standard) IPA(key) | /naː˧.jok̚˦˥.rat̚˦˥.tʰa˨˩.mon˧.triː˧/(R) | |
นายกรัฐมนตรี • (naa-yók-rát-tà-mon-dtrii) (classifier คน or ท่าน)