My Thai wifes passport is due for renewal on the 15th Aug 2010.

We would like to travel to the UK in late April.  She thinks she remembers reading something about once receiving your new passport you have to wait 6 months before you can apply for a visa with it ?

I can't find anything on the passport web site about this so has anybody got any information on this matter  ?   

Maybe she means the passport must still be valid for longer than 6 months before you leave the country. Like the passport expires on Aug 15, and you had until Feb 15 if you wanted to go abroad with this passport. In this case it's better to apply for a new one, then have the visa put on the new one.

Correct, the only rule I can think of is that the passport is valid for at least 6 months if she wants to enter another country.

Thank's everyone, I think you are correct with your comments, depending on the red shirts we will be going up to Bangkok Tuesday to try and renew her passport, if there is a waiting time I will post the information they gave on here when we get back