Myriotrema thailandicum is a species of lichen in the family Graphidaceae.

Found in Thailand, it was formally described as a new species in 2002 by lichenologists Natsurang Homchantara and Brian J. Coppins.

The type specimen was collected from Namtok Phlio National Park (Chanthaburi Province) at an elevation of 100 m (330 ft).

Here, on a trail close to the Phlio waterfall, it was found in a lowland rainforest, growing on both rocks and tree trunks.

The lichen has a smooth and shiny, greenish-grey thallus with a dense cortex and a white medulla.