Prepare water in Ball Waterbath Canner. Heat jars in simmering water until ready for use. Do not boil. Wash lids in warm soapy water and set aside with bands. 

Combine the vinegars, water, sugar, and salt in a 4-quart saucepan and bring to a boil, stirring to dissolve salt and sugar. 

Place 1 clove crushed garlic, ½ teaspoon each mustard seeds, and black peppercorns into a hot jar. Pack beans cut side up, add onion slices, 2 Thai chilis, and 2 sprigs dill into a jar.

Ladle hot brine over beans in a jar leaving a ½ inch headspace. Remove air bubbles. Wipe jar rim. Center lid on the jar and apply band, adjust to fingertip tight. Place the jar in a boiling water canner. Repeat until all jars are filled. 

Process jars for 15 minutes, adjusting for altitude. Turn off heat, remove the lid, let jars stand 5 minutes. Remove jars and cool 12-24 hours. Check lids for seal, they should not flex when the center is pressed.