The Department of National Parks, Wildlife and Plant Conservation has found a way of protecting the environment and making money -- by selling the rubbish left behind by visitors.

Natural Resources and Environment Minister Varawut Silpa-archa said on Tuesday that visitors will be given a black plastic bag to collect their rubbish, which they must give to rangers when they leave the park.

The trash will then be sorted, with recyclable items sold and money earned added to the park office's coffers.

This idea was inspired by the death of a wild deer in Khun Sathan National Park in northern Nan province. The deer, estimated to be about 10 years old, apparently died from consuming 7 kilogrammes of plastic waste and an item of underwear.

In a statement, Mr Varawut blamed the death not on plastic, but the people who use it.

The adult deer, weighing about 200kg, was found near the park office and appeared to have died several days ago.

The plastic waste found in the animal's stomach included coffee and instant noodle packets, plastic bags, rubber gloves, handkerchiefs, underwear and plastic rope. Park rangers assumed that the deer died of constipation and old age.