I just came back from a trip to REP.
On PG: BKK-REP r/t is USD 360
On 3K: SIN-REP r/t is USD 230
Both inclusive of taxes.
If you are arriving from elsewhere in the world, SIN has better pricing options than to connect via BKK.
Unfortunately, if you insist on Skyteam, the only connection is via Ho Chi Minh.