Bring vinegar, sugar, and mustard seed to simmer in small saucepan on medium heat. Reduce heat to low; cook 5 minutes. Remove from heat. Let stand 5 minutes to cool. Pour over chopped peach in small bowl; toss gently to coat. Refrigerate 1 hour or until chilled.
Meanwhile, rinse and drain lentils. Place lentils, water, and sea salt in small saucepan. Bring to boil. Reduce heat to low; cover and simmer 20 minutes or until tender. Remove from heat and uncover. Cool to room temperature in remaining liquid. Drain.
Mix drained lentils, oil, 1/2 tablespoon of the chives and thyme in medium bowl until blended.
Spread about 1 teaspoon crème fraîche on toasted baguette slice. Top with about 1 tablespoon lentil mixture and 1 teaspoon Pickled Peach. Garnish with remaining chives.
