It was identified as his is Medythia suturalis (Motschulsky), a widespread and common species in weedy farmland throughout SE Asia, from India to Ryukyu Islands and the Philippines, as far east as Sulawesi. For illustration and references see Kimoto (1989) Galerucinae of Thailand, Cambodia, Laos & Vietnam: 104-5 and fig. 28c (p.102). One of the references listed by Kimoto may include the biology. However, it belongs in the ‘luperini’ and, therefore, is certain to have the larva feeding cryptically, on roots in soil, or stem-boring.