Is investing in STI ETF (via RSP) worth it, particularly when there’s talk of a coming recession in Singapore?

Truth be told, it is very difficult to time the market and catch the bottom even if there's a recession because a low can go lower. The benefit about RSP is that it takes out the emotions when investing and helps you buy regardless of market conditions. If there is really a recession, you will buy more units since the prices are cheaper now. One recommendation I would give is to consider global / overseas market for greater diversification apart from STI ETF.

If you are doing dollar cost averaging, you should not have to worry about a coming recession because if a recession does come, you will be buying more unit of sti etf. If a recesion does not come, you will still be buying into the sti etf. In the long run, your sti etf units prices will rise along with the market.