Some disgruntled farmers have also threatened to block roads if their plight remains ignored.
In Surin, more than 5,000 farmers gathered in front of the provincial city hall and complained the problem had dragged on for more than four months.
Similar payment problems have been reported in other provinces.
In Phichit, farmers are calling on those in nearby provinces to join their protest to step up pressure on the government.
These farmers plan to block the Pluak Soong Intersection on the Asia Road in Phichit’s 8 Wachirabarami district.