Paracanthocobitis phuketensis can be diagnosed from all its congeners by combination of the following characters: lateral line incomplete, ending near dorsal-fin insertion; dorsal fin with 9½-10½ branched rays; usually absence of axillary pelvic lobe, occasionally rudimentary; series of black blotches, sometimes overlain with faint dusky stripe along side of body not obscuring lateral blotches, ending near caudal fin; circular black spot on upper margin of caudal-fin base; black pigment not extending from black blotches along side of body onto base of pectoral fin; absence of marmorated pattern anterior to dorsal-fin origin; dorsal saddles longer than interspaces, frequently connecting to lateral blotches; upper caudal fin with 7-8 branched rays (Ref. 117351).