JAKARTA • Even by the standards of a country known for frequent regulatory surprises, Indonesian President Joko Widodo's policy gymnastics on palm oil has been extraordinary.

The world's biggest producer of palm oil announced a sweeping ban on cooking oil shipments late last week to curb domestic shortages.

That sent global prices surging on Monday, but the market was relieved when reports emerged from Jakarta that only exports of palm olein, a refined product, would be halted.

Two days later, the government delivered another shock, saying the ban would be even wider and also include crude palm oil.

It was not the first time that President Widodo has blindsided commodity producers, traders and investors.

The biggest exporter of power-station coal paused shipments earlier this year to secure dwindling supplies, and it is also considering an export tax on some nickel products.

Mr Widodo wants to move Indonesia up the value chain by processing more raw materials at home.

The strategy has had some success, most notably in the battery metals space, and it resonates with voters who elected him for a second five-year term in 2019.

Balancing his resource nationalism and desire to protect Indonesians from rising prices against the need to woo more offshore funds to finance his ambitions is tricky, however.

The palm oil episode shows how disruptive and poorly communicated policy can alienate investors.

"The flip-flop and protectionist policy will tarnish Indonesia's reputation and standing as an attractive foreign-direct investment destination", particularly in agriculture, energy and exports, said Maybank Investment Banking Group's senior economist Chua Hak Bin.

The sprawling tropical archipelago has endured a long history of foreigners plundering its resources that dates back to the Portuguese seeking spices in the 16th century.

Mr Widodo's strategy is a response to that, although the coal and palm oil interventions have been more about cushioning poorer Indonesians from the impact of the commodities boom and surging inflation.

The palm oil export ban is meant to ensure there is ample supply of cooking oil priced at 14,000 rupiah (S$1.34) a litre, but will be a drag on the wider economy. It is likely to shave around US$2 billion (S$2.8 billion) off exports and cut economic growth by 0.15 to 0.2 percentage point for each month it stays in place, Goldman Sachs Group said in a note.

The country is targeting gross domestic product growth of 4.8 per cent to 5.5 per cent this year.

Policy uncertainty has risen over the past few months as the scope of action widened beyond the value-add strategy, said Mr Vishrut Rana, an economist at S&P Global Ratings in Singapore.

That is a challenge for commodity firms, given the country is a big producer of palm oil, coal, nickel, copper and rubber, he said.

That uncertainty could also threaten Indonesia's ability to hit investment targets.

The government is aiming for total foreign and direct investments of as much as US$131 billion for next year, around 6 per cent higher than this year.

Indonesia's efforts to attract funds from offshore have been hampered in the past by corruption and excessive red tape. Mr Widodo has sought to improve the climate with his so-called omnibus law that was introduced in 2019, but that now must be revised because of court orders.

In the metals space, Indonesia is trying to leverage its mineral deposits to become a hub for battery and electric vehicle production.

It is looking at banning or taxing shipments of various metals and is also requiring foreign investors to build smelters onshore rather than just extracting raw materials and processing them elsewhere.

These policies seem to be bearing fruit. Chinese nickel producers like Tsingshan Holding Group are adding projects, and the total number of operational mineral smelters is forecast to rise to 53 next year, from 19 early this year. South Korean conglomerates Hyundai Motor Group and LG Energy Solution are building a US$1.1 billion electric vehicle battery plant, with commercial production expected to start in 2024.

The palm oil ban might not move the needle much on current decisions on Indonesia, given investors are already accustomed to policy shifts, according to Mr Wellian Wiranto, an economist at OCBC. But the chaotic implementation does leave a "bitter taste in the mouth", he said.

BLOOMBERG