The Sept. 7 trading session delivered one of the most dramatic reversals seen recently in Vietnam’s stock market.

The VN-Index gained more than 12 points at one stage in the morning, climbing above 1,860 and moving toward the historic 1,900-point threshold. Selling pressure, however, quickly spread across the market. By the close, the index had fallen 31.44 points, or 1.7%, to 1,821.64.

Declining stocks overwhelmingly outnumbered gainers, with 458 falling against just 231 advancing. Trading value on the Ho Chi Minh Stock Exchange, or HoSE, reached nearly VND17.2 trillion ($654 million). Foreign investors also returned to net selling, unloading nearly VND500 billion ($19 million), with VCB, CTG, VIC, SHB and DXG among the main targets.

Most notably, large-cap stocks - particularly the “Vin” group, which has been a major driving force behind the VN-Index in recent months - came under simultaneous pressure.

VIC briefly reached an all-time high of VND265,000 ($10.08) per share before reversing course and falling VND11,100 ($0.42) to close at VND245,000 ($9.32). VHM lost VND700 to finish at VND74,500 ($2.83). In contrast, VPL rose to VND81,100 ($3.08), while VRE climbed to VND27,000 ($1.03).

VIC has experienced sharp swings in recent months, falling steeply before rebounding and repeatedly setting new record highs. The latest decline may not necessarily change its longer-term rally. Since the beginning of 2025, the stock has still risen more than 12-fold.

That means an investor who theoretically put VND1 billion ($38,000) into VIC at the beginning of 2025 and held the shares throughout the period would now have an investment worth more than VND12 billion ($456,000).

VIC’s extraordinary rally has also dramatically reshaped the fortune of Pham Nhat Vuong. According to Forbes, as of Sept. 7, the billionaire’s net worth had fallen by about $1.6 billion from the previous session to $37.8 billion.

Even so, Vuong remained Southeast Asia’s richest person and ranked among the world’s 60 wealthiest billionaires.

Behind Vingroup’s new valuation may lie a much bigger story. The conglomerate is accelerating its shift from real estate toward industry, led by VinFast alongside investments in technology, energy, infrastructure, semiconductors, artificial intelligence and robotics.

In the first six months of 2026, Vingroup reported net revenue of VND222.3 trillion ($8.45 billion) and after-tax profit of VND20.375 trillion ($775 million), up 72.5% and 4.5 times year on year, respectively.

However, the Sept. 7 session also exposed the downside of a market heavily dependent on a handful of mega-cap stocks: when VIC and VHM reverse course, the VN-Index can fall rapidly even when the broader market is not weakening to the same extent.

Market upgrade remains a catalyst, but pressure is mounting

The Sept. 7 decline raises a broader question: Is the Vietnamese stock market’s rally truly sustainable? For now, there may be no definitive answer.

One of the market’s most important catalysts is FTSE’s upgrade of Vietnam from frontier to secondary emerging market status, scheduled to take effect on Sept. 21.

FTSE Russell has announced a list of 27 Vietnamese stocks to be included in the FTSE Global All Cap Index. VIC, VHM and VCB are among the large-cap stocks, while BID, HPG and VPB are classified as mid-caps.

The move represents an important step that could open the door wider to international capital, particularly from investment funds and exchange-traded funds tracking FTSE indexes.

The VN-Index has already surged into the 1,850-1,900 range, while market liquidity has not fully kept pace with the index’s gains. Capital has remained concentrated in a handful of heavyweight stocks rather than spreading broadly across the market - a cause for concern.

When VIC, VHM, VCB or several major banking stocks rally sharply, the VN-Index can easily reach new highs. But when those stocks correct simultaneously, demand elsewhere in the market may not be strong enough to absorb the selling. The Sept. 7 session offered a clear example.

Meanwhile, bank deposit rates remain relatively high, at around 8-10% a year based on rates observed in the market, potentially competing with equities for investor capital.

Oil prices are another variable to watch. On the afternoon of Sept. 7, WTI crude had climbed above $92 a barrel, while Brent was approaching $98, raising inflation risks and putting additional pressure on expectations for global monetary policy.

The key question for the market after Sept. 21, therefore, may not simply be whether stocks rise or fall, but whether new capital inflows will be large and broad enough to reduce the VN-Index’s heavy dependence on a small number of heavyweight stocks.

The Sept. 7 session offered a clear warning: when buying demand weakens and market leaders reverse course, a market that appears exceptionally strong can quickly descend into a sell-off.

According to MBS Research, the trading week in mid-September will be pivotal as decisions by the U.S. Federal Reserve and the Bank of Japan could combine to create a “double impact” on global liquidity flows.

For the Fed’s Sept. 15-16 meeting, the probability of an interest-rate increase has surged to nearly 65%, with the U.S. central bank maintaining a firmly hawkish stance.

Attention will then turn to the Bank of Japan’s Sept. 18-19 meeting. An indirect liquidity shock could emerge if the BOJ tightens monetary policy, potentially triggering an unwinding of yen carry trades.

As the yen strengthens, global investment funds may move away from riskier assets to repay yen-denominated borrowing, creating indirect net capital outflow pressure on emerging and frontier markets such as Vietnam.

The combined effect of these two monetary forces could act as a filter that drives speculative capital out of the market, while redirecting investor attention toward developments involving market infrastructure and structural reforms.

Manh Ha