A survey of the whirligig beetles of the genus Patrus Aubé, 1838 occurring in Thailand belonging to the newly designated Patrus landaisi species group is presented. Three new species are described and illustrated: P. garuda sp. nov., P. nanensis sp. nov. and P. phetchabunensis sp. nov.; with P. apicalis (Régimbart, 1891), P. landaisi (Régimbart, 1892), and P. subapicalis (Ochs, 1930) stat. nov. being recorded for the first time in Thailand. Morphological and molecular analyses, together in an integrative approach, support the elevation of P. subapicalis to species status, instead of being a subspecies of P. apicalis. A diagnosis, illustrations of habitus and diagnostic characters, distribution maps, habitat images and a key to species are provided for all known members of the P. landaisi species group that occur in Thailand. A checklist of species in the group is also given.