Thai 'Koh Samui' spore print

The Thai Koh Samui is one of the most iconic and historically important Psilocybe cubensis strains from Southeast Asia. Collected directly from the wild on the tropical island of Koh Samui in the Gulf of Thailand, this strain represents the original genetics that put Thai cubensis on the world map. Its dense, stocky fruiting bodies, warm caramel-brown tones and deeply rooted cultural backstory have made it a cornerstone variety in any serious cubensis collection.

Discovered on a Legendary Mushroom Island

The island of Koh Samui has been synonymous with magic mushrooms for decades. Psychoactive fungi — locally known as "hed keequai" (laughing mushrooms) — have been used by native Thai communities on the island for centuries, both in spiritual ceremonies and as part of everyday rural life. It was during a series of field expeditions between 1989 and 1991 that American ethnomycologist John W. Allen, together with Hawaiian botanist Mark D. Merlin, systematically documented the occurrence, harvesting and use of psychoactive mushrooms on Koh Samui and the neighbouring island of Koh Pha-Ngan. Allen collected specimens of Psilocybe cubensis growing in buffalo dung across the island's lush pasturelands and brought these genetics to the West — giving rise to the strain we now know as the Koh Samui. His research was published in the Journal of Ethnopharmacology in 1992, making it one of the earliest academic papers on psychoactive mushroom use in Thailand.

Thai Koh Samui vs. Thai Ban Hua — Same Island, Different Strains

Our catalogue includes two Thai strains from Koh Samui, and the differences between them are striking:

• Thai Koh Samui (this strain): The original wild collection. Produces short, stocky, densely packed fruiting bodies with thick stems and heavy caps — the classic "Fatass" phenotype. A robust, aggressive grower with a compact, powerful build.
• Thai Ban Hua: A hybrid between Ban Hua Thanon genetics and an unknown Thai cubensis variety. Produces tall, slender fruits with slim stems and perfectly round caps. More refined and elegant in appearance, with denser mycelium and faster colonisation.

Where the Ban Hua is the graceful hybrid, the Koh Samui is the raw, wild original — broad, heavy and built for the tropical heat. Together they illustrate two very different expressions of Koh Samui island genetics.

Visual Characteristics of Thai Koh Samui

• Cap: 45+ mm in diameter. Caramel to reddish-brown, lightening towards the edges. Shape varies from bell-shaped and round to flat, sometimes with a pronounced central nipple (acute umbo). Caps are thick and fleshy.
• Stem: 50–120+ mm, but characteristically short and thick relative to many other cubensis strains. White to yellowish in colour, bruising blue when touched.
• Overall appearance: Compact, dense and powerful. The Koh Samui is a stocky strain — its short, thick stems and heavy caps have earned it the famous nickname "Fatass" among cultivators and collectors worldwide.

Tough, Tropical and Built to Thrive

The Koh Samui's tropical origins have made it one of the most heat-resistant cubensis strains in existence. It thrives in warm, humid conditions that would slow down or stall many other varieties, and its aggressive mycelium colonises substrates with strong rhizomorphic growth. It performs well on a wide range of substrates — from grain and brown rice flour to manure-based and coir-based blends — and rewards collectors with consistent, generous flushes of dense, heavy fruits. Spore deposits are dark brown to nearly black, producing rich, clearly defined prints with excellent long-term viability. The original Koh Samui genetics have also given rise to several famous descendants, including the Koh Samui Super Strain (KSSS), demonstrating the quality and stability of this foundational lineage.

How to Use a Spore Print

Not sure where to start once your spore print arrives? We have put together a detailed guide that walks you through the entire process, from scraping spores off the print to preparing them for microscopy or long-term storage. Read our step-by-step instructions here: How to Use a Spore Print.

Why Add Thai Koh Samui to Your Collection

If you are building a diverse Psilocybe cubensis collection, the Thai Koh Samui is the essential Southeast Asian wild classic. No other Thai strain carries the same combination of genuine wild provenance, documented academic history and iconic status. Its dense, stocky fruits, warm tropical colouration and legendary "Fatass" phenotype make it one of the most recognisable cubensis varieties in the world. Whether you are drawn to its deep roots in Koh Samui's mushroom traditions, the pioneering fieldwork of John Allen, or the powerful, compact build that made it famous, the Koh Samui belongs in every serious spore library.