A long-tailed macaque passed out for 10 hours after drinking strong coffee from an unattended plastic bag hung from a tourist's motorcycle in Bangkok's Bang Khun Thien district on Sunday.
The "Khon Rak Ling Hua Jai Kraeng" Facebook community page reported the incident, in which the male six-month-old monkey fell sick after drinking the stolen coffee drink.
Alerted by a food vendor at the Khun Kala Floating Market that a juvenile monkey appeared sick, a Khon Rak Ling Hua Jai Kraeng team along with a veterinarian went to transport the animal for medical treatment at the nearby Doctor Raiwin Pet Hospital.
The little monkey, which passed out from a severe reaction to caffeine, was given a mixture of carbon and saline until 3am on Monday.
After its recovery, the group released the monkey in the vicinity of its troop, although they said they would monitor its health.
The group also advised members of the public who visited areas frequented by long-tailed macaques to give them only fruit and vegetables at designated areas, rather than throwing food on the road, which had led to many monkeys being killed in road collisions.