Just wanted to ensure I understood correctly on the commission. Will probably stick to SGD 4000 every 3 months
OK, but at that pace Interactive Brokers is probably more attractive for you. Let's do the math....
1. To buy S$16,000 worth of IWDA via Standard Chartered, with buys every 3 months, you'll need to pay approximately 0.8% (let's be very generous to Standard Chartered -- Tangent314 just reported their currency conversion cost is higher than that) (S$128 = about US$95) in currency conversion costs and US$42.8 (US$10.70 x 4) in brokerage commission costs. That's US$137.80 per year.
Plus you have the loss associated with delaying each purchase to "batch up." Let's suppose that IWDA has an average long-term yield advantage (versus holding short-term cash in Singapore) net of all costs of 4% per year. One third of your funds are delayed by 2 months, and another third are delayed by 1 month. A one month delay costs about 0.33%, so here's the calculation:
S$16,000 divided by 3 = S$5,333.33
S$5,333.33 multiplied by 0.33% = S$17.78
S$17.78 multipled by 3 = S$53.33 = about US$40
So your total expected annual cost of investing S$4,000 per quarter in IWDA via Standard Chartered is about US$177.80.
2. With Interactive Brokers the calculation is a lot simpler. At this level of investment flow (S$1,333.33 per month) your minimum and your maximum commission for both the currency conversions and the IWDA purchases, monthly, is US$10 until your total account value reaches US$100,000. So that's US$120 per year. You also have a very, very tiny currency conversion cost owing to the tight spread that IB offers. Let's overestimate that tiny spread and call it 5 basis points (0.05%), so rounded up that's about US$5 per year. Total annual investment costs at IB: US$125, or about US$50 less expensive than Standard Chartered.
We are not counting the reverse path in retirement (selling shares of IWDA, converting U.S. dollars to Singapore dollars, transferring Singapore dollars to a bank account in Singapore) in this comparison, but the reverse path is also more attractive from Interactive Brokers based on these respective two companies' current commissions and fees. And we're not counting the "cash drag" cost at Standard Chartered since evidently you've got to keep a minimum balance in a regular Standard Chartered account to avoid a fall below fee and to do business with their brokerage arm -- I believe I'm stating that requirement correctly.
Anyway, net net, IB is the lower cost choice for you.