SEOUL, May 20 (Reuters) - Samsung Electronics' ( SSNLF )

labour union plans to embark on a massive 18-day

strike on Thursday after bonus payment talks with management

collapsed and attention is now focused on whether the government

will issue an emergency arbitration order.

Some 48,000 people plan to walk off the job with significant

consequences for the South Korean economy and the supply of

memory chips globally, and the government flagged at the weekend

that such an order is possible.

Here are some things to know about the potential order:

WHAT HAVE AUTHORITIES SAID?

A South Korean government official said on Wednesday that

talk of emergency arbitration is premature and that there was

still time for dialogue.

The government is seen as union-friendly as President Lee

Jae Myung is a former youth labourer who was injured on the job.

But Lee said on Wednesday that a certain union was "crossing

the line" when it claimed a share of a company's operating

profit even before income tax is paid.

"There is a role for the government when anyone crosses the

line to make sure they conduct themselves responsibly for the

good of the larger community," he told a cabinet meeting.

WHAT DOES THE EMERGENCY ORDER INVOLVE?

An emergency arbitration order has been invoked just four

times in modern South Korean history. It puts a strike on hold

for 30 days and requires both sides to continue talks mediated

by the government's National Labor Relations Commission.

The government can resort to such an order if it considers a

strike would result in "significant injury to the national

economy".

If the commission considers that mediation has failed, the

next step is an arbitration process under a separate panel that

will hear from both parties before making a binding decision.

Anyone refusing to comply faces up to two years in prison or

a 20 million won ($13,300) fine.

The last time the measure was invoked was in 2005 when

Korean Air pilots walked off the job but agreed to a compromise

pay hike after four days.

WHAT IS THE POTENTIAL IMPACT OF A SAMSUNG STRIKE?

Samsung accounts for almost a quarter of the country's

exports. It is also the world's largest memory chip maker and

production disruptions could dent global supply at a time when

the AI boom has caused shortages.

The strike could in a worst-case scenario shave 0.5

percentage points off a forecast 2.0% expansion for the South

Korean economy this year, according to an official from the

country's central bank, who declined to be named.

South Korean officials have also said a major disruption of

production at Samsung Electronics ( SSNLF ) would translate to up to 1

trillion won ($665 million) in daily losses for the company.

COULD THERE BE POLITICAL FALLOUT?

South Koreans go to the polls on June 3 to elect mayors and

governors across the country and the strike has the potential to

sway swing districts. Currently, Lee's liberals are expected to

dominate.

The liberals are wary that they may lose labour votes, their

traditional support base. Lee also wants to capture the moderate

Gyeonggi province, which has seen its economy boom thanks to the

tens of thousands who work at Samsung facilities there.

Samsung's union, launched just two years ago, is not

affiliated with any of South Korea's major labour federations

but some of the more established and militant unions have vowed

to act in solidarity.

($1 = 1,504.9000 won)