It is endemic to Borneo and currently only known from its type locality in the Kelabit Highlands of Sarawak, Malaysia,[3][4][5] but presumably, it also occurs in the adjacent Kalimantan, Indonesia.

[3] The specific name eok is Kelabit for "tiny" and refers to the small size of this species.

[4] Kalophrynus eok is only known from the holotype,[4][5] an adult male measuring 26 mm (1.0 in) in snout–vent length.

[2] The holotype was found in primary submontane forest at an elevation of about 1,050 m (3,440 ft) above sea level.

The specimen was calling from a water-filled node of a bamboo plant fallen across a forest path.