Probably my first question here:

My passport expires 10 oct 2007 and I got a new retirement extension last week at Immigration Bangkok valid until passport expires. (not a full year thus, also got multiple re-entries until oct 2007)

I will go to my home country in may 2007 for one month.

Do I need to get a new passport there and come back with old passport with extension in it?

Do I need to do something to get the full year or request extension from oct 2007 onmwards?

I also notice that a passport need to be valid for at least 6 months when entering the kingdom.

I have a trip to Sillypore planned in March 2007 and wil not have 6 month left on my return.

Makes me wonder what to do...

Apply for and pick up the new passport with your country's embassy in Bangkok. Subsequently,

visit the immigration office to transfer your extention-and re-entry stamps to the new one.

As long as your p/port and your re-entry permit is valid you can return to Thailand and the 6-months' rule does not apply. (Had, however, once to ask for a manager as the airline staff did not know this when checking in for Thailand.)