Actually this is their 3rd go.
First was back in 1983 or 1984, twice weekly Colombo-Singapore-Jakarta Tristar service. Lasted about a year.
Then again the same service in 1992/1993. Lasted about a six months or so, they ended it on " aircraft shortage grounds"
And then in 1998, they codeshare with Emirates on its 777s on the Colombo-Singapore-Jakarta routing. Emirates fly the route four times a week(but only code share with UL to Jakarta twice a week). And then as demand grew from a business and leisure base, SriLankan decided to mount its own twice weely service, with A330s via Singapore. Of course, they operate on different days to the Ek service.