Two new species, Piper durionoides Suwanph. & Chantar. and P. kongkandanum Suwanph. & Chantar. (Piperaceae), are described from southwestern Thailand. Piper durionoides is characterized by a persistent stylelike spine or echinate and glabrous infructescence. The distinguishing characters of P. kongkandanum combine vegetative and reproductive organs. This species has pilose or velutinous branchlets with uniseriate hairs. The floral bracts are hairy at the base and ciliate at the margin, and fruits are connate for 3/4 length on rachis. The description and illustration are presented. The IUCN conservation status of both species is assessed as VU, or Vulnerable.