Nongpanee Mahadthai, performing under the stage name Ja R-Siam, 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 last 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.

In 2013, Ja joined the label Rsiam.