Catalyzes the reaction that attaches fucose through an O-glycosidic linkage to a conserved serine or threonine residue in the consensus sequence C1-X-X-S/T-C2 of thrombospondin type I repeats (TSRs) where C1 and C2 are the first and second cysteines of the repeat, respectively (By similarity). O-fucosylates sporozoite proteins CSP and TRAP (By similarity). O-fucosylation regulates stability and intracellular trafficking of TRAP but not of CSP (By similarity). Dispensable for parasite transmission to the mosquito vector and/or infection of the vertebrate host hepatocytes (PubMed:31334132). GDP-beta-L-fucose + L-seryl-[protein] = 3-O-(alpha-L-fucosyl)-L-seryl-[protein] + GDP + H(+) GDP-beta-L-fucose + L-threonyl-[protein] = 3-O-(alpha-L-fucosyl)-L-threonyl-[protein] + GDP + H(+) Protein modification; protein glycosylation. In S.stephensi mosquito vector, number of oocysts in the midgut, number of sporozoites in the salivary glands, and sporozoite gliding motility are normal (PubMed:31334132). Infection of mouse host is normal including invasion of hepatocytes and infection of erythrocytes (PubMed:31334132). Belongs to the glycosyltransferase 68 family.