Two Australian tourists sparked outrage when they turned up at a Thai airport wearing nothing but matching leopard-print Speedos and flip-flops.

The pair - one with pink trunks and the other in orange - are believed to have been on a nearby beach when they remembered they had a flight to catch on the island of Phuket, Thailand, on January 30.

A shocked passenger took a picture of them as they pushed trollies with their backpacks to the airport entrance to check in for their flight back to Perth.

However, they are believed to have been ordered to cover up shortly after walking into the packed building.

Vietnamese tourist Bui Thi Huong, who said he saw the two men at the airport, joked: 'They looked like they had come straight from a beach party.

'It was funny but it wasn't appropriate clothing for the airport with other members of the public around.'

Officials said they had not identified the tourists or taken any action against them. They are believed to be from Australia.

However, shocked locals criticised airport security for lax enforcement of rules while others expressed disapproval towards the foreigners for what was perceived as a lack of respect for Thailand.

Nit Panan said: 'In foreign countries, lawbreakers are usually arrested and fined with a warning. However, they are aware that Thai authorities tend to be lenient, leading to incidents such as peeing on a Tuk Tuk, peeking out of taxi windows, wearing only underwear in a temple, or running through red lights.'

Fuengfah Passaweeanon added: 'I would like to caution them to be mindful of Thai regulations and to show respect towards Thai people. 

'We are not an uncivilised country, so they should refrain from doing anything that the hosts of this country would not do.'

Other locals said the holidaymakers appeared relaxed and there were many others on the island like them who were 'just enjoying their vacation'.

Yo Chob Ye said: 'Given that their countries experience cold temperatures, they might find it difficult to restrain themselves when enjoying the hot weather in Phuket.'

Nattaya Leepon added: 'I hear that they had just finished playing in the water and hurried to the airport to change their clothes in the toilet before flying back to their country.'