in which kingdom will you place an organism which is single celled, eukaryotic and photosynthetic?

According to 5 kingdom classification, the main criteria for classification include cell structure, thallus (body) organisation, mode of nutrition, reproduction and phylogenetic relationship. According to this classification all the single celled eukaryotes have been placed under the kingdom Protista. For example Euglena, which is a single celled, eukaryotic and photosynthetic has been placed under this group. So the organism described by you will also be placed in the same kingdom.