On the grounds of morphological characteristics and molecular phylogeny of the fungus, G. siamensis belongs in phylum Ascomycota, class Leotiomycetes, but cannot be referred to any accepted order at this time; i.e. it has to be treated as incertae sedis within the class. It is conceivable that future molecular data on this and other genera of Leotiomycetes might indicate that a new order is appropriate, but we consider that this would be premature at this time.