Muan Jai Design Starbucks Tumbler Muan Jai (ムアンジャイ) means "heartfelt happiness" or "heart-filling" in Northern Thai (a dialect of Northern Thailand). I purchased this at an event held in Marunouchi previously. I dropped it several times, so there are cracks on the surface. Coffee or other liquids will not leak, but please refrain from purchasing if you are sensitive about this.