Bet for value on this river?

Its an easy check! You have a really weak Pair with 5x and even with lets say Q5 i would not be betting again since your opponent is either likely to have a weak 9x but a weak 9x he'd prolly bet the Turn with but he might have a bunch of 6x that he didnt dare to be betting with, hoping you'd barrel off with some drawing hand and on the River some unlikely but possible 3x Combos got there. With 6x with a decent kicker i would valuebet again but with just third pair no Kicker and a possible straight on the board, you should check. The reason for betting is more that you might expect him to be folding a better hand than you expect him to be calling a bunch of worse hands. But i dont think he's fold 6x here since you could have some 7x 8x type of gutshot hands that you follow through with.

ahhhh i've just seen that he was openraising preflop. i first thought he was donking into you and then decided to check. So thats a big difference since since he's been the aggressor and he checks the turn and calls off your bet, he's likely to have Ax a good amount of the time and he will rarely have x3, occasionally k3 A3 but really rare times. So since i said you could barel with T8 7x 8x gutshot type of combos, i see him frequently calling off your riverbet. So i would go for thin value again!

further questions that you have? feel welcome to post more of your hands!