Euphorbiaceae Trigonostemon pachyphyllus Airy Shaw Laos, Khammoune prov., Boualapha distr., Nong Seng village, Vang Phae Lay mountain, around point 17°31'02.7"N, 105°47'17.2"E. Primary dry evergreen and semideciduous broad-leaved forest on very steep rocky slope near karstic hill top composed with solid, marble-like highly eroded limestone at 300-530 m a.s.l. Undershrub 1.5 m tall in open place in open place at hill base. Flowers dark red-purple. Not common. 11 May 2018, L. Averyanov, Khang Sinh Nguyen, T. Maisak, Littideth Xaiyavongsa, Siphanom Keovankham, AL 924.