The Customs Department has tried to allay fears about a request for passengers to declare valuables before leaving the country, saying it is only a voluntary matter designed to help people returning to the country with the same items.

The request, made under Customs Announcement No 60/2018 and signed by Customs Department chief Kulit Sombatsiri on Feb 26, has raised eyebrows as it is thought it could cause problems for outbound travellers.

Outbound passengers with valuable items, such as watches, cameras or laptop computers, which have serial numbers that can be verified, can report to customs officers in the outbound passenger zone, he said.

They need to give two photos of each item to officials as well, he said.

After officials check the items, passengers will be issued documents listing the valuables to present to Customs when returning to the country.

The requirement has sparked criticism, particularly in social media.

Mr Kulit said the department is only suggesting that people taking valuable items out of the country declare them with customs officials so there is official proof that they have done so.

This measure is to prevent problems arising if they are randomly searched when returning to Thailand so they can prove the items are personal property and not bought abroad immediately prior to returning, he said.

The full 'suggestion' list is on the Customs Department's website.

It includes this notice:

"WARNING: The information in this website is intended as a general guideline only and subject to changes without prior notice."

People can decide whether or not to declare the items as this is not a legal requirement, Mr Kulit said.

Customs Department deputy director general Chaiyut Kumkun said the controversial request is not new.

It was part of an old regulation which was issued under the 1926 Customs Act, he said.

The old Customs Act was repealed and has been replaced by the 2017 Customs Act. As a result, old items under the old law were revoked so the department has to issue new announcements covering the same details, he said.