Both malaria treatment and prophylaxis target the parasite dihydropteroate synthase (DHPS) and dihydrofolate reductase (DHFR) enzymes. Specific point mutations in these genes confer resistance to sulfadoxine-pyrimethamine (SP) in both Plasmodium falciparum and P. vivax. We used direct sequencing to examine the prevalence of point mutations in pvdhps and pvdhfr in 160 P. vivax isolates collected from areas along the international borders of Thailand. Results show that the majority of the isolates harbored a quadruple mutant allele of pvdhfr and a double mutant allele of pvdhps, but the distribution was not uniform. The highly mutant allele combination was especially prevalent along the Thai-Myanmar border, whereas the majority of the isolates from areas along the Thai-Cambodian and Thai-Malaysian borders carried double mutant alleles of pvdhfr and single mutant alleles of pvdhps. Novel mutations that have not been identified previously at codon 512 of pvdhps (K512M, K512E, K512T) were also found.