I recently was in Jomtien late afternoon. There were zero people in the information office so I took the opportunity to speak to the two immigration officers there. I spoak to them at length about the need to get a new TM30 after a trip abroad. I was asked for my passport and asked if I had a current TM30 in my passport. They looked at it and they both agreed, without hesitation, that there was no need for a new one.
My 90 day is due next month so I will test what I was told.