To date, the genus Diaphera Albers, 1850 was represented by a single species (D. prima Panha, 2010) in Thailand, and another (D. saurini Benthem Jutting, 1962) was known from Cambodia. Here we report D. prima for the first time from Cambodia, and describe two new species (D. pongrati, new species, D. parini, new species) from Eastern Thailand. Both new species live sympatrically with D. prima, which is reported here from Chachoengsao, Chon Buri, Rayong, and Sa Kaeo Provinces.