Polypropylene (PP) bags (plastic, petroleum product, recycleable, reusable) and other variants come in a bewildering array of sizes and shapes. It makes the most sense to source locally for Thai-made (or already-in-Thailand) rice/grain bags, since their is a very large industry requiring these.
Most Chinese firms have very large order requirements, but based on caluclating the area needed with standard 18" x 30" (or close) rice bags (45cm x 75cm) and ending up with 5" x 20" wall area, this gives 0.7 feet per bag. Taking care to not stumble over the metric to foot calculations, this means 143 bags per 100 square feet of wall. Given an 11 meter diameter (which works out to 36 feet), that is a circumference of 113 feet multiplied by a 9 foot wall results in 1,017 square feet of wall. This is just under 1,500 bags.
It turns out that bag sizes are not really standardized in terms of shape and size (or rather, there are many standards). At first look there were two companies making bags (that show up in a Google search in English, likely there are many more).
The China Woven Bag website (with bags much too expensive) provides a great deal of information about the bags. The main points to make are that the weave, how the plastic is treated (waterproofed one or both sides), whether/what kind of printing on the bag, and of course the volume of the order.
The main point here is that it makes economic and ecological sense to find used bags which are not damaged and still quite appropriate for the building material.