You must have a line coming into the tank from the nahm papa meter(Pranburiwater).This should feed your water tank.is this flowing freely?If so the pump should work as long as there's water in the tank.I have had a house in hua hin (hin lek fai)we do occasionally run out of water.what make of pump is it?If it's playing up the bosch makita shop on petcasem rd is good for repairs