Melt butter in a medium saucepan over medium-high heat; swirl until butter foams. Add bell pepper and thyme; sauté 3 minutes. Add corn; sauté 2 minutes. Add milk, flour, and salt, stirring with a whisk. Cover; bring to a boil. Reduce heat to low, and simmer 15 minutes, stirring occasionally. Place 1/2 cup corn mixture in a mini food processor; process until smooth. Return to pan; stir well.