The STI declined in 5 waves from its all-time high, which means an eventual re-test of the lows cannot be ruled out. Although the medium-term wave-count is unclear to me, here's the chart and trendlines.
Recent breakdowns were on strong volume, which warns of distribution. Any further upside in the near-term will likely be limited to max 3250. Most recent decline broke below an uptrendline(black). Expect near term support at bottom channel line(maroon).
Break below 2670 = Dire Straits!
Crucial level for STI would be 2670, a sustained break below will change the medium-term outlook to bearish. Further support is around 2520/2420.
All the best!