Well I was having the same problem getting to BKK. I just purchased the Fare from DFW-SIN for arounnd 950 for April. I was able to Purchase a B fare on CX from SIN-BKK-SIN for around 200. I get AA miles all the way and can upgrade from DFW-NRT-DFW with VIPs. The trip gets me 21288 status miles or 43000 total miles for around $1100.