I’m planning on moving to Thailand and rent for a year, (next March) I work away for 3 weeks then back to Thailand for 3 weeks, do I still need a visa ? Any help much appreciated

I have been working overseas and traveling to Thailand quite often for my days off, for several years now, entering on visa exempt stamps in my Canadian passport without any issues until now ( I normally spend 10 days here at a time, not working, no business interests). I arrived at Suvarnabhumi last week and was told at immigration that I have a System Alert. The immigration official told me that next time I need a visa, because I come here so often. Any other FIFO/offshore workers had a similar issue recently? Is the System Alert a serious problem?