The five small parties are Action Coalition for Thailand, Chartthaipattana, Palang Thongthin Thai, Thai Forest and Land Reclamation, and People Reform parties.
The five small parties have a combined 14 votes in the House of Representatives, while the PPRP has 116 seats.
Six other parties led by the PPRP have 130 seats, which is still far short of the 251 needed to form a majority government in the 500-seat House of Representatives.