A notorious zoo where the ‘world's loneliest gorilla' is kept has reopened following a refurbishment.

Pata Zoo, located on the sixth and seventh floors of a high-rise shopping mall of the same name, underwent renovations last year before welcoming visitors again on March 3.

Footage shows newly-painted cages at the controversial attraction. Its most famous inhabitant, the 33-year-old female gorilla Bua Noi, wandered around inside her enclosure with the sad, lonely eyes that she has become known for.

Bua Noi, which means little lotus, was imported from Germany in 1990 when she was only a year old and has never left the cramped zoo.

Animal rights groups have slammed the alleged inhumane conditions that Bua Noi has endured but the zoo's executive claim they treat her well. They denied that they attempted to negotiate or sell the primate following claims in October last year they 'will only release world's saddest gorilla for $780k'.

The owner of the Pata Zoo reportedly told Thai environment minister Varawut Silpa-archa that he would only allow Bua Noi to die peacefully around other gorillas for 30 million Thai baht, around 782,000 USD.

Thanetpol Thanaboonyawat, secretary to the minister of Natural Resources and Environment, said that the government department had been organising charity fundraising events but failed to raise enough funds to meet the owner's demands.

He said that officials want to move Bua Noi to a sanctuary to spend her last days around other gorillas at a sanctuary in Germany.

Meanwhile, zoo chiefs insist that the refurbishment proves they take care of the animals. They said that Bua Noi is staying in her cage alongside different species of monkeys, albino primates, and chimpanzees in nearby enclosures.

Bua Noi's plight first emerged in 2015 when animal rights activists handed in a petition which called for Bua Noi's release and the zoo's closure.

In 2015, officials of the Department of National Parks, Wildlife and Plant Conservation ordered the zoo to close after it was found to lack the correct paperwork.

However, it eventually re-opened and kept the gorilla.

PETA Senior Vice President Jason Baker said previously that Bua Noi was being forced to live in 'horrifying and cruel conditions' and suffering 'extreme psychological distress'.