Dear dorothy dix,
Not looking good for quite a while yet, the civil engineers in my Bangkok based company support the suggestion that it will be at least 4 weeks or more of major flooding covering most of Bangkok. Given what's been happening over the last few days I have doubts that any part of Bangkok will be given any special treatment. Many sections of the the Chao Phya river are above the flood walls and the river is not that far away from the Silom / Suriwongse areas.
Can I encourage you to go to:
Thailand News - Thailand Forum
If your not a member, it's a very easy sign up and free. Lots of comprehensive details on the floods.
Good luck.