The draft was rejected by 38.65 per cent of the voters who exercised their right, the EC added.
It said invalid ballot constituted 3.15 per cent of the turnout.
The election watchdog said the three southern border provinces had the highest rates of invalid ballots – 7.43 per cent in Pattani, 7.11 per cent in Narathiwat and 6.54 per cent in Yala.
Bangkok saw the least percentage of invalid ballots or just 1.53 per cent, the EC added.