looping

Here goes...I'm English in BKK, got a non-imm type 'o' visa based on marriage, and a work permit; both valid until April 2011. I resigned from my job in BKK and have taken a job in Phnom Penh. I want to visit soon to secure a condo (and a shipping address)...
Question 1: When my BKK school cancels the WP, can I still keep the visa if I get a multiple re-entry permit? I'll be visiting every month or 2 to see the missus etc. NB I'll be able to show funds coming into Thailand from Cambodia every month as International Bank Transfers so in theory will still have income coming into Thailand (more than 40k) as the requirement states.
If I can't keep the visa without the WP then I won't bother with the re-entry permit because I'll move over there for the new semester on July 25th so can just come back between my initial trip and the 25th on a tourist visa.

Next issue: Only about 1 1/2 pages left in passport.
Question 2: If I apply for a new passport now can I still use the existing passport in a week or so when I go to PP for the accom search?
Question 3: Is there a 'fast track' passport service available in BKK? Better to go to the British Embassy or send direct to HK?
Question 4: Finally, is the full page Cambodian visa multiple entry or single (if it's multiple maybe I can squeeze it all on my existing passport).
I think that's it...
Thanks for reading, any info would be much appreciated!