泰
タイ, た, はす, ひろ, や, やす, やすし, ゆたか, よし
peaceful, calm, peace, easy, Thailand
JLPT1 G7 S10 F1281
The relevant seal inscription form is 大# great + an element combining 水 water and 廾 pair of hands (→ action indicator) → great outpouring of liquid (compare 太) → *calm*; *peace* (← relaxed feeling ← plenitude). *Thai(land)* is via transliteration (泰, or 泰國).
[Full Kanji Etymology List]