A monkey became best friends with a cow and constantly rides on its back in Thailand.

The female macaque named Lilly reportedly wandered away from its troop and into a pasture in Lopburi province, central Thailand.

Farm owner Lampung Srimuang, 45, noticed the primate perched casually on one of her cows, which was grazing on the field at the time.

At first, Lampung tried scaring the monkey away, but it held its ground and would continue to show up riding the same cow the next morning.

She then called forestry officers to deal with the stubborn simian, fearing she might be arrested for illegally possession of protected wildlife.

The specialists released it into the forest, but Lampung was surprised to see Lilly back the very next day – atop her favourite bovine friend.

Local authorities advised Lampung to let the monkey be and not try to sell or hurt it. Today, the docile Lilly helps Lampung watch over her cattle, catching and eating pests like mites or mosquitoes that bother the livestock.

Lampung said: ‘This macaque is like family to us. We named it Lilly and let it walk freely with the cows.

‘I remember a troop of monkeys visiting my family’s property to find food. All of them left the next day, except for Lilly.’