Well in a way the rules were written sense, thicket of blades says it would, but ride by attack says it wouldn't. Thicket of blades mentions withdraw and five foot steps by name, but also just says any movement. I find the way it says any movement to be ambiguous and therefore side in the case of ride by attack.<br/><br/>In a balance sense having thicket of blades work on ride/fly by attacks and tumble is just too much power for something that is a 3rd level ability. Especially sense the others require multiple feats, or skill checks that can fail.<br/><br/>In a logic sense, attacks of opportunities happen when the person's guard is down. Like if they were trying to get away and be defensive. A ride by attack is an attack, the attackers guard is not down.