Unusual, but possible, if, for example, there was an aircraft/vehicle moving on to/ encroaching the runway. Usually, go arounds occur prior to the threshold, but if something started to move on to the runway subsequently, or the pilot or controller noticed the encroachment later than normal, that could easily explain the late overshoot. Generally aircraft can overshoot right down to touchdown, and, depending on the runway length/weight etc, for a short time afterward. The event you describe should be no cause for the level of alarm described, but pax can be a sensitive lot. I would think- not being an airline pilot myself- that it would be too late for an overshoot in most situations once the brakes were on and reverse thrust operating.
In this case, whatever the reason, the pilot appeared to take the safer of the options available. Try writing to Thai and ask for an explanation.