if you see termite trails then you'd better do something quick

what i do is to drill holes into the frame starting from floor level and see how bad it is. then, inject termite pesticide into the holes. patch up holes with putty.

also, you can drill holes into the ground below the frame to inject pesticide. this will only keep them away, so check other wooden stuff around

termite pesticide can get from hardware shop but read the labels carefully cos some are hazardous/carcinogenic