To get around the stopover problem, do the following.

Confirm the oubound flights to SIN. Such as IAD-LAX-SIN

Keep all the other sectors open and show a stopover at each connecting city.

Such as SIN-BKK stop BKK-FRA stop FRA-IAD stop. Chances are 99% that you will have no problem connecting all the way thru from BKK.

Also, if you want to really confuse them, do two more open sectors from SIN to KUL and rip them out before you leave from BKK.

The hidden city police wont have a clue.

Good luck!