i posted initially at r/personalfinance but had no response. https://www.reddit.com/r/personalfinance/comments/2ww2rq/sg_local_country_index_not_as_diversified/

I will give as much info as i can, and i hope you can tell me your thoughts Im a long time lurker, and this is my throwaway account. Im 28 year old singapore guy. I earn 60k SGD(50k USD) per year. I watched the 'best investing' video shared here a few days ago and there's a point where the host speaks about a time where Cisco was about 10% of an index and that's a bad thing. It got me thinking, Singapore's Index is STI and it consist of the 40 largest company in singapore. The problem is the top 4 holding weight is 42% and I am not comfortable with this anymore. (source http://www.spdrs.com.sg/etf/fund/fund_detail_STTF.html#[1] ) My country has a mandatory social security vehicle whereby 20% of my pay is automatically saved into an account yielding 4%/year, and my employer will match 17%. (my income 60k SGD/yr, 12k is deducted from my income, and the employer adds 10.2; so im 'forced' to save 22.2k per year into this account) this forced savings account cannot be touched until im at my retirement age(65yrs old). this is a very simplified version of the social security here. I see the forced saving of 22.2k as some sort of a bond investment so my personal investment; all 120k of it is currently in STI. Moving forward, i am going to invest about 2k per month. My costs right now is brokerage fee 0.25% and the fund's expense ratio of 0.3% I am considering of switching to something along the line of 40% US(Vanguard VTI) 40% International (Vanguard VT) and 20% Local (STI) The problem is the brokerage give PATHETIC exchange rate, they're pocketing about 1.21%! so i see this as added cost to buying VT and VTI. Is my thinking right, that in the long run, i am saving money because even with the 1.21%(+another 1.21% when i sell it way into the future) exchange rate spread, my cost is lower because VTI's expense ratio is 0.05%pa where as the index im holding onto now is 0.30%pa? Also exchange rate risk, is it something i shoud be worried about? i mean, even the local index is subjected to exchange rate risk because the profit is derived from all over the world. so it shouldnt be any different right? What do you guys think?