Nongpanee Mahadthai (born May 6, 1991) (Thai: นงผณี มหาดไทย), performing under the stage name Ja R-Siam (Thai: จ๊ะ อาร์ สยาม), is a Thai singer and model.

Ja graduated from Rajamangala University of Suvarnabhumi.

Ja is well known for her 2011 single cover, "Kan Hoo", the singer became a subject of heated debate in previous years over her lewd dance moves and risque puns.

Though most of her success as a recording artist has been in Asia, Ja has also gained popularity in Western countries, due in part to internet videos which have gone viral.

[1] Media outlets have referred to Ja as "Star of the Sexually Explicit".