The UTMB World Series Returns to the Thai Jungle
The Amazean Jungle Thailand by UTMB takes over the city of Betong, in the southernmost province of Yala, from April 30 to May 3, 2026. Set on the Thai-Malaysian border around the iconic Mongkollit Tunnel, the event brings five competitive distances to a region that has quickly carved out a reputation as one of Asia's most demanding tropical ultras.
Weather Conditions: Heat, Humidity, and Tropical Showers
Late April and early May fall right at the tail of the pre-monsoon transition. Daytime temperatures in Betong typically settle around 30°C, but the dense rainforest pushes humidity above 85%, with felt temperatures climbing close to 40°C in exposed sections. Rain is part of the recipe: short tropical downpours can turn forest tracks into mud rivers within minutes, while the canopy keeps trails wet long after the showers stop.
Heat acclimatization, salt management, and waterproof packing are non-negotiable. Race organizers consistently flag hydration discipline as the leading cause of early DNFs.
Course Difficulties
The 2026 edition spans the full UTMB stone spectrum:
- Betong 100M: 116 km with 5,570 m of positive elevation gain, technical singletrack and very long jungle sections under the canopy.
- Tunnel 100K: 91 km and 3,870 m of D+, including the signature crossing of the historic Betong tunnel.
- Jungle 50K: 55 km and 2,200 m of D+, an intense humid loop that punishes every early pacing mistake.
- Mist 20K and Flower 20K: shorter introductions to the terrain, still packing 900 m and 400 m of climbing respectively.
The mix of slick roots, muddy descents, exposed climbs, and tropical wildlife gives the Amazean its identity. Cut-off times are strict, especially on the 100M, where many runners face the heat of a second day.
Our Favorites for the Betong 100M
The men's lineup is headlined by Japan's Yutaro Yokouchi (adidas Terrex JP, UTMB Index 814), fresh off a runner-up performance at Tarawera Ultra-Trail by UTMB 2026. He faces serious resistance from China's Xiao Lin (Kailas Fuga, 777) and Yue Cui (775), and from Canada's Jeffrey Campbell (T8 Elite, 795), a multiple ultra champion in Southeast Asia. Among the home favorites, Sanya Khanchai and Danon Rattanatumrong (adidas Terrex Thailand) know the Betong terrain inside out.
In the women's race, China's Liping Wang (Aonijie, Index 730) is the clear pre-race favorite ahead of compatriots Xueer Shang and Jiangrong Yuan (Rossignol). Malaysia's Siok Har Lim (Kailas Fuga) is the regional contender to watch.
Tunnel 100K: a Stacked Asian Field
The 100K may produce the deepest race of the weekend. Chinese veteran Peiquan You (Anta, Index 876) carries the favorite status, but Kristjan Chapman (Iceland, Fuga Mountain Club, 840), recent winner of the Malaysia Ultra-Trail by UTMB MY100, looks ready to challenge him. Man Kumar Roka Magar (Nepal, Kailas) and Vietnam's Chinh Ngo (Kailas Fuga and Suunto) add altitude pedigree to a tropical course.
For the women, Nepal's Priya Rai (T8, Index 739) and China's Hua Rong Fu (689) head the entry list, with Canada's Elisabeth Petit (Ultranomades) and Kenya's Prudence Maseki (Trail Runners DXB) lining up to disrupt the order.
Jungle 50K and 20K: Speed in the Heat
The Jungle 50K features one of the strongest fields of the weekend. Tao Luo (China, adidas Terrex, Index 890), recent winner of the Ultra-Trail Shudao DSD 100K, will battle Salomon China's Huohua Zhang (Index 891), Sheng Zhang (876) and Japan's Yamato Yoshino (855) in what promises to be a tactical chess game in the heat. On the women's side, Slovakia's Veronika Leng (Anta Guanjun, 787) and Belgium's Vanja Cnops (T8, 686) headline a varied international lineup.
Over the shorter distances, Thailand's Parattakorn Suppalapwattana (Brooo Athlete) and France's Quentin Vieville (Brooo) are clear favorites for the Mist 20K, while France's Angelique Lesport (Salomon Réunion, Index 655) and Canada's Francis Boutin (Ultranomades) will be hard to beat on the Flower 20K.
What to Watch
Beyond the podiums, the Amazean Jungle Thailand by UTMB has become a defining stop on the Asian trail running calendar. The combination of dense jungle scenery, oppressive heat, and a deeply international elite field makes for a weekend where pacing, hydration, and mental resilience matter as much as raw speed.