That's a naive statement. Banks there are paying that high a rate because most likely, there is an inflationary threat or the local currency is/was or will be further devalued. In the long run, there is usually no net incentive to do this with the exception that the funds are invested in some highly appreciating assets like stocks/bonds/real estate. I don't follow local markets there at all so...
Edit: Having said that, if your situation were such that you are *intending* on returning to your country to live there permanently again, then the whole situation would be different and the rate situation would be telling you to put your money in some hard assets there now for a good return 5-10 years down the road, but again, I don't follow SriLanka.