Now for the correct answer. 1157 bulbs have 2 circuits or should I say 2 hots that share a chassis ground. So when that ground is lost and the park lamp circuit is hot the current uses the turn circuit for a ground . Result is park lamp current feeding back through the turn circuit thus lighting the indicater on the dash.
Your problem is a loose fixture etc.. at right front. Can't be the rear fixture since that turn circuit is interupted at the turn signal switch so it can be brake lights instead.