SUVperb, I assumed from “HDB interest” that you mean a HDB loan. Is that what you mean, or is that $50K of remaining mortgage a bank loan? If a bank loan, what’s the interest rate?
I’m still wondering if there’s a spouse, partner, or elder in the picture. Henry’s suggestion about a Retirement Account top up is also a good one. A Retirement Account top up will outperform an accelerated HDB loan repayment in investment terms. Both are liquidity reducing, but it looks like you have decent liquidity. Also, you currently have at least $90.5K of room for a Retirement Account top up, so you have the option to allocate more than $50K (your outstanding mortgage amount) to the effort if you wish.
By the way, Singlife is currently offering 2.5% interest on up to $10,000 per person deposited with them, SDIC protected. Even that’s a better deal than an Ordinary Account repayment for that amount because the interest is computed daily (not based on the lowest monthly balance), and it can be withdrawn at any time without disrupting the 4.0% earning Special Account. Singlife can change the 2.5% interest rate at any time, but for as long as it lasts it’s nice.