The Indonesian shareholders of Bumi Plc are confident they can shake up the miner's board and remove co-chairman Nat Rothschild before creating the world's biggest coal firm, major investor Samin Tan said on Tuesday.

Tan and Indonesia's Bakrie Group, who together own 29.9 percent voting rights in Bumi Plc, said last Friday they were seeking to oust financier Rothschild and other key directors from the board of the London-listed coal miner. They require more than 50 percent approval from shareholders.

We are very confident, otherwise we wouldn't have done what we have done, because we believe we have the vision to help beautify the asset, Tan told Reuters in an interview, adding he had already talked to some institutional shareholders.

The attempted coup by Tan and the Bakries to cut out Rothschild from a firm he helped set up may worry investors already concerned about governance at Bumi, owner of some of the richest mines in Indonesia, the world's biggest exporter of thermal coal.

Bumi is the most closely watched firm in Indonesia and instability at its network of companies is seen as a symbol of the continued risks of investing in the G20 economy, which recently won a return to investment grade status.

But Tan said he would cut Bumi's debt and create shareholder value.

We just want to achieve a board that is cohesive, collaborative, Tan said, adding that he had seen media reports of discord between Rothschild and the Bakrie Group. He said he hoped Rothschild would remain a shareholder.

Tan in November paid $1 billion (632 million pound) to enable his coking coal firm PT Borneo Lumbung Energi & Metal to get a 23.8 percent stake in Bumi Plc. He said the move to change the Bumi Plc board was mutually agreed with the Bakrie family during that deal.

Rothschild owns just under 12 percent of Bumi Plc.

Shares in Bumi Plc fell further after Tan's comments, trading 3.15 percent lower by 1317 GMT.

If the changes sought by the Bakries and Tan are approved by shareholders at a general meeting to be held by March, Tan would become Bumi's chairman and the Bakrie Group's Indra Bakrie would become co-chairman.

Bumi's CEO Ari Hudaya, a long-time Bakrie lieutenant, would be replaced by another Bakrie mining executive, Nalinkant Amratlal Rathod.

Indonesian investment firm Recapital Advisors via its unit Bukit Mutiara has 13 percent voting rights in Bumi Plc. The Bakries' Indonesian listed miner Bumi Resources, now a unit of Bumi Plc, has lent money to both Recapital and Bukit Mutiara.

If Recapital sides with the Bakries and Tan at the general meeting, they would have 43 percent of the votes. Other shareholders in Bumi include BlackRock Advisors and the Abu Dhabi Investment Council.

Tan said he was heading to London next week to meet shareholders and Bumi's directors.

Last year's move by Tan to invest in Bumi Plc, which helped the politically connected Bakrie Group pay off the bulk of a $1.35 billion loan, marked the second time in three years that the Bakries have scrambled to complete a deal to ease debts.

Rothschild, the future Baron Rothschild of a European banking dynasty, put his reputation on the line by enabling a joint London listing of the Bumi group.

COAL SUPERPOWER

If Tan becomes Bumi Plc chairman, he said he would use his experience of developing Borneo Lumbung's greenfield mine to push for faster execution of Bumi projects, such as the Bakries' Bumi Minerals Resources plan to start zinc production from north Sumatra, which he said should come by 2014.

He also would like to see a merger between Indonesian coal miners Bumi Resources and Berau Coal Energy, possibly via a share swap, in a deal that could be worth $7.5 billion based on Reuters calculations.

Tan said the aim was to more than double their current combined annual output of 85 million tonnes to 185 million tonnes a year by 2016, which would dwarf other coal producers such as BHP Billiton and Xstrata.

Bumi Plc owns 29 percent of Bumi Resources and 85 percent of Berau. Tan envisages these two firms forming a coal unit, with the Bumi Minerals Resources, considered by some analysts as holding their most promising assets, as another non-coal unit.

I think to combine Berau into Bumi Resources, I think it's a good thing to do, said Tan. If everything goes well, we could probably see it quite imminently.

HUMBLE

Tan, 46, who came from a family of fish traders on Sumatra island, dropped out of university to become an accountant taught maths to students to make ends meet. He later set up an investment firm with $2.7 million and then bought a coking coal mine.

He debuted late last year on Forbes Asia list of the 40 richest Indonesians with an estimated net worth of $940 million, though still uses a battered Blackberry phone and proudly showed off a hole in his sock.

He admits he took on risk to join the Bakries from the comfort of Borneo Lumbung, a highly profitable and previously debt-free coking coal miner that aims to double output from 5 million tonnes this year to 10 million by 2014.

Concerns over the Bakrie Group's corporate governance and use of leverage have weighed on the share prices of Bumi Resources, and Borneo's shares too since his deal for Bumi Plc.

Tan, considered by some analysts as a subordinate partner to the powerful Bakries, is looking to stamp his mark by changing a history of mounting debts at Bumi Resources by slashing its annual cost of funds to 8 percent from 14 percent now. He said such a move would also cut fees for investment bankers and save around $300 million a year.

Credit Suisse is the Bakrie Group's main banker.

I'm sure you've heard in the market that we are the Bakries. We're not the Bakries, Tan said.

(Editing by Richard Borsuk and David Cowell)