I've had stamps placed on other pages in my passport where there was room for a stamp. Usually some location to place a stamp even if it touches a few old ones.
My mistake,I meant to say that the TM30 can be stamped at immigration upon every entry into Thailand without applying for a new TM30,i.e. The TM30 can be used over and over until visa expiration date.
Immigration at the Promenade Mall in Chiang Mai told me the that when I apply for another nonresident O visa after the current visa expires that I will need a new TM30.
In Chiang Mai just bring your previous TM30 to immigration within a couple of days of your arrival back to be stamped. It's valid for the length of your visa. No need for a new TM30.
You should not have a problem. If your destination is Chiang Mai you should file a TM 30 at immigration within a couple of days after arriving or you will likely receive a Baht 1600 fine when you go to Chiang Mai immigration for your 30 day extension