Five poachers were arrested on Wednesday morning inside Kaeng Krachan National Park in Phetchaburi when park officials found langur carcasses on them.
Mana Permpoon, chief of the national park, said the five were spotted by a patrol carrying five fertiliser bags.
The officials found 27 pieces of langur in the bags.
The five included two l6-year-old males, a 50-year-old woman, and two men, aged 43 and 19. They are residents of Tambon Padeng.
They claimed they went into the park to collect wild honey.
The five were handed to the Kaeng Krachan police.