Your William H had brothers Samuel Edward Thomason and Louis.In 1920, William and Louis were living together.Louis Belia Thomason died July 2, 1958 in Butte County.
The 1920 Census for Kyrene, Maricopa County, AZ William H. Thomason, age 49(1870/1871), born in Mississippi Maud, wife, 38, born in Texas Winnie, 22; Nellie 19; Sam, 16; Katie 13, all children born in Texas Louis B. Thomason, age 33, born in Mississippi.
The 1930 Census for San Bernardino, San Bernardino County William Thomason, age 60(1870) born in Mississippi Maud N, 48, brn in Texas, farmer/truck farm Kate M. Davidson, daughter, age 24 Joe A. Davidson, son-in-law, 28 Patricia M Davidson, Grand-daughter, age 3 11/12, born in CA.
It is VERY possible this is the gravesite of your William Thomason.
Be patient, sometimes people that try to help, need a lot of help themselves.A lot of help.I'm just trying to put some common sense and accuracy back into searches.
There is a volunteer on the Random Acts of Genealogical Kindness, Christine, that "might" be able to give you some suggestions: http://www.raogk.org/californ4.htmhttp://www.raogk.org/californ4.htm