UPDATE 2-Rain-hit Bumi Plc slips to underlying loss

* Operating profit $128 mln vs $62 mln

* Underlying loss $117 mln vs $54 mln profit

* Restructuring a "work in progress"

* Shares drop 4.5 percent

By Clara Ferreira-Marques

LONDON, Aug 9 (Reuters) - Indonesia-focused coal miner Bumi Plc slid into the red in the first half of 2012, weighed down by rising costs and the impact on production of heavy rain in Indonesia's Kalimantan province in the first months of the year.

The miner, co-founded by financier Nat Rothschild, also warned persistently low thermal coal prices would dent profitability in the second half, as contracts set with higher prices run out.

Thermal coal prices have been battered this year, hitting a two-year low in June. A boom in global coal supply has coincided with a flood of U.S. exports, as U.S. gas prices at record lows make gas a cheaper alternative for domestic power generation.

Bumi posted steady prices for the first half - coal from unit PT Berau was sold at $76.6 per tonne on average, while coal from part-owned PT Bumi was sold at $88. That compares to $74.6 and $91.3 per tonne last year respectively.

But prices given for the bulk of production over the year implied a significant drop in the second half.

Bumi said 18 million tonnes of Berau's 2012 production, forecast at 20 to 22 million, had been priced at $70 per tonne, while PT Bumi's expected production was priced at $80-$85.

The company was confident prices would rise in the longer-term, however. "All research indicates that prices cannot be sustained at this level," Chief Executive Nalin Rathod said, pointing to chronic power shortages in places like India, a major consumer of thermal coal, where major outages last month left hundreds of millions of people without grid power.

"Demand cannot be what it is today and prices cannot be what they are today," he added.

The miner, one of the world's largest thermal coal exporters, listed in London over a year ago but its share price has dragged, hit by boardroom scuffles, worries over debts at its subsidiaries - and also by its complex structure.

Rathod said efforts to streamline the company, which could see separately listed Berau and PT Bumi merge to create a coal arm, were "work in progress". Bumi Plc owns 85 percent of Berau and 29.2 percent of Bumi Resources.

He added the group could sell non-core assets - including a stake in base and precious metals miner Bumi Resources Minerals , held through PT Bumi - to help pay down debt.

"We have to monetise to reduce some of our debts. In this market it is not easy, but we are working on that," Rathod said. "BRM is not a coal asset, so if we are calling ourselves a coal company, we have to see this as non-core."

Bumi, which told the market last month it would be hit by adverse weather, said its operating profit more than doubled to $128 million in the first half, but its bottom line was hit. It posted an underlying loss of $117 million for the six months, against a $54 million profit a year earlier.

A large part of the drop was caused by rain and flooding in Kalimantan, which hit production and squeezed margins. Bumi Plc cut production estimates for Berau to 20-22 million tonnes for 2012, from 23 million, but its 2014 targets remain.

Cost pressures, however, would ease in the second half, it said, thanks to lower fuel prices and improved production.

Bumi's shares were down 4.5 percent at 353.4 pence at 1132 GMT, underperforming a flat UK mining sector.