I think SQ new SIN-LAX-SIN route will follow its SFO direct service with a departure out of SIN in the morning (after the first few flights from several key transit markets like India, Jakarta, Kuala Lumpur and Perth arrive) and arrives in LAX in the morning. The return flight will depart LAX in the late morning / early afternoon and arrives in Singapore in the early evening to enable connection to the same key transit markets.

The direct service will most likely begin on 1 Dec 2018 as Airlineroute tweeted that the existing first class section of ICN-LAX flight will not be available for sale on 1 Dec 2018 and the discounted economy fare between ICN-LAX also disappears from that date.