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
If you want to travel in and out of Thailand as you visit other countries I'd suggest a multi entry Tourist Visa. Valid for 60 days but unlike the single entry you can come back to the Kingdom should you desire .