How many Thais does it take to scrub a tank ?

One can do it
But things go easier with two. One inside, one outside.
At my house the numbers double, and so does the cost.

My water tanks collect rainwater for the swimming pool and gardening. They get an annual scrubbing during the rainy season. That way you know the resupply of water is imminent. It's a humid, sweaty and very dirty job. The bottom four inches of water are solid black.

Meanwhile moving the entrance gate into the property is also under way. Once the gate is moved into the property, guest will have covered parking for their motorcycles, and will remove them as traffic obstacles in these narrow streets.