sentences:  For an area to qualify as a "thesaban tambon", it must have a gross income of at least 5 million baht and a population of at least 5,000 with a minimum density of 1,500 per km², plus the approval of the population within that area.Many of today's "thesaban" municipalities were originally "sukhaphiban tambon", sanitation districts, the number of which had grown to 35 in 1935, when these were converted into municipalities.New sanitary districts were again established starting in 1952.