Both Brazil and the U.S. have issued protests over a Thai legal ban against imported commodities and food with residues of the weed killer paraquat and the pesticide chlorpyrifos. The ban will prevent billions of dollars of trade in wheat, soybeans and some foods. The two countries have asked Thailand to instead follow Codex maximum residue levels. Thailand had also threatened to ban the use of glyphosate. Some other countries ban domestic use of paraquat and chlorpyrifos but not imports.  One point of leverage is Thai rice exports. Rice is a heavier user of plant protection products than wheat or soybeans and it is the top agricultural export by Thailand. In fact, one of Bangkok’s goal is to become a larger exporter of rice. Me...