The Indonesian rupiah has fallen through the psychologically significant level of 18,000 per US dollar, leading investors to closely monitor whether the central bank will implement more forceful countermeasures.

The currency declined by as much as 0.5% on Thursday, bringing its cumulative loss for the year to approximately 8%. Analysts from BNP Paribas, MUFG Bank, and PT Mega Capital Sekuritas anticipate that Bank Indonesia will intensify its market interventions and could potentially raise interest rates again as soon as this month.

Parisha Saimbi, a strategist at BNP Paribas, noted that Indonesian authorities have historically defended key round-number levels, and 18,000 is likely to be a psychological threshold that market participants will watch closely. The central bank's intervention actions appear aimed at curbing the pace of the currency's depreciation.

The rupiah is the worst-performing currency in Asia this year, partly due to market concerns that elevated oil prices will increase energy subsidy costs, thereby widening Indonesia's budget deficit. A breach of the 18,000 level could accelerate foreign capital outflows from the local stock and bond markets, making this threshold a critical test for policymakers seeking to restore market confidence amid growing economic headwinds.

Investor confidence in Indonesian assets has deteriorated this year. MSCI Inc. previously warned the country could be reclassified as a frontier market, while Fitch and Moody's have downgraded its sovereign rating outlook. Additionally, there is growing market apprehension over the government's attempts to tighten control over key commodity exports.

Stabilizing the rupiah is a key task for Bank Indonesia, according to Lloyd Chan, a foreign exchange strategist at MUFG Bank. Given the currency's depreciation trend, the central bank may be compelled to hike rates again in June, with Chan forecasting a potential increase of 50 basis points.

Bank Indonesia has already deployed a series of measures to support the local currency and attract capital inflows, including issuing rupiah-denominated notes and tightening requirements for US dollar purchases. Last month, the bank surprised markets with a 50-basis-point rate hike, and its next policy decision is scheduled for June 18.

In a statement released on Wednesday, the central bank affirmed it will continue to stabilize the rupiah in the market and utilize all available policy tools to maintain foreign exchange liquidity and support financial market stability.