Common names: Leaf beetle.
Distribution: India, Thailand, Laos, Cambodia, Vietnam.
Image locations: Mae Hong Son
Additional notes: Identification comments Michael Geiser "I think you're correct with Lema trifasciata Jacoby, 1908 . According to the key (Kimoto & Gressitt 1979), the labrum should be black and the outer black stripe reaches the margins of the elytra (as opposed to L. externevittata). Also, the elytral pattern matches with the drawing for L. trifasciata."
Images of Lema (Lema) trifasciata from Thailand.