They together reported profits of $1.16 billion in Q1 this year, down from $1.64 billion in the same period last year, the South Korean company’s financial statements showed.

Samsung Display Vietnam’s profit of almost $299 million last year turned to a loss of $49.14 million this year.

Samsung Electronics Thai Nguyen, the largest of the four, saw profits fall by 5 percent. Samsung Electronics Vietnam, also known as Samsung Bac Ninh, reported a steeper fall of 22 percent.

The two plants in northern Vietnam produce half of all the cellphones the corporation ships globally.

Samsung Ho Chi Minh City CE Complex, which produces TVs and other home electronics items, was the only one to buck the trend as profits zoomed by 44 percent.

But the good news for Samsung is that its profit of $1.16 billion in Vietnam in the first quarter reported a big turnaround from Q4 last year when it was only $100 million, the lowest in years.

For full-year 2018 profits fell by 20 percent to $4.7 billion, with the Thai Nguyen company reporting a 30.6 percent decline.

Samsung, the world’s biggest smartphone maker, is the largest foreign investor in Vietnam. It employs around 160,000 people.

It exported goods worth an estimated $60 billion from Vietnam last year, up 12 percent from 2017, accounting for a quarter of Vietnam's exports.

Its Vietnamese subsidiaries’ sales of $67 billion represented 30 percent of its global revenues.