Two closely related yeast strains, ST-382 and ST-392, isolated in Thailand showed intermediate relatedness in the DNA-DNA hybridization experiment suggesting that the two strains represent closely related distinct species. In the tree based on the D1/D2 domain sequences of the large subunit rRNA gene, the two strains are located in a subclade in the Wickerhamomyces clade with high bootstrap support. In the D1/D2 domain, the two strains differed by two nucleotides and are assumed to be very closely related. Strain ST-392(T) (=BCC 15102(T) = NBRC 107799(T) = CBS 12176(T) forming hat-shaped ascospores is described as Wickerhamomyces tratensis sp. nov. and strain ST-382(T) (= BCC 15093(T) = NBRC 107800(T) = CBS 12175(T) is described as Candida namnaoensis sp. nov. because ascospores are not found in this strain. In phenotypic characteristics, W. tratensis and C. namnaoensis are discriminated by the ability of alcoholic fermentation and the assimilation of galactose, D-xylose and D-gluconic acid.