Typification Details: Holotype XAL, Allen, 8 Aug. 1991
Host-Substratum/Locality: On sandy-clay soils in rice paddies and meadows: Thailand
This species, known only from Thailand, grows on rich soil in meadows (Guzmán et al. 1993). It presents basidiomata like P. mexicana R. Heim, with pileus 7-15 mm diam., lamellae adnexed and stipe 40-65 × 1.5-2 mm, without annulus.
Basidiospores 10-13 × 6-8 µm, rhomboid to subrhomboid in faceview, thick-walled. Pleurocystidia 16-20 × 5-6.5 µm, scattered, sublageniform, hyaline and cheilocystidia 18-28(-30) x (5-)5.5-7(-8) µm, sublageniform, sometimes branched.
Basidiospore morphology supports P. samuiensis within sect. Mexicanae Guzmán. Molecular analyses by Borovička et al. (2011) that show this species as separate from sects. Cyanescens and Semilanceatae support sect. Mexicanae as independent.