Place ground beef in medium skillet.
Brown over medium-high heat.
Drain.
Remove beef from skillet; set aside.
Place 2 tablespoons Oil in same skillet.
Add onion and garlic.
Saute over moderate heat until onion is tender.
Stir in ground beef, tomatoes, salsa, chili powder, coriander, thyme, salt, cayenne and cumin.
Cook over medium-low heat, stirring occasionally, 10 to 15 minutes, or until mixture is thickened.
Remove from heat.
Stir in refried beans.
Heat 2 inches Oil in deep-fryer or large saucepan to 375 °F.
Meanwhile, place 1/2 cup beef mixture in center of each tortilla.
Fold opposite sides of tortilla to center over beef mixture.
Fold ends toward center; secure with wooden pick.
Fry 1 to 2 chimichangas at a time, 1 1/2 to 2 minutes, or until golden brown.
Drain on paper towels.
Sprinkle top of each chimichanga with 2 tablespoons Monterey Jack cheese (optional).