เจ้าอยู่หัว

Etymology
From 🇰🇲; literally meaning:
 * (a) "lord above [all/our/my] head[s]",
 * (b) "lord at [all/our/my] head[s]", or
 * (c) "[one with] lord on the head".

The suggested meaning (c) is based on the traditional belief that a future Buddha has a figure of Lord Buddha upon his/her head.

Noun

 * 1) (พระ~, สมเด็จพระ~, พระบาทสมเด็จพระ~)

Usage notes

 * In modern usage, the term is preceded by when applied to a monarch who has been formally crowned, and by  when applied to a monarch that has not or not yet been formally crowned.