Folding TPTK for one bet on river and not so scary board?

[Lunkan]

Button is 18/15/1.0
CO is 60/0/0.86

Party Poker 2/4 Hold'em (6 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

Preflop: Hero is SB with A[img]/images/graemlins/spade.gif[/img], K[img]/images/graemlins/spade.gif[/img]. UTG posts a blind of $2.
<font color="#666666">1 fold</font>, CO calls, <font color="#CC3333">Button raises</font>, <font color="#CC3333">Hero 3-bets</font>, UTG (poster) calls, CO calls, Button calls.

Flop: (12 SB) A[img]/images/graemlins/heart.gif[/img], 3[img]/images/graemlins/spade.gif[/img], 9[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(5 players)</font>
<font color="#CC3333">Hero bets</font>, UTG calls, CO calls, Button calls.

Turn: (8 BB) T[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(5 players)</font>
<font color="#CC3333">Hero bets</font>, UTG folds, <font color="#CC3333">CO raises</font>, <font color="#CC3333">Button 3-bets</font>, Hero calls, <font color="#CC3333">CO caps</font>, Button calls, Hero calls.

River: (20 BB) 6[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(4 players)</font>
Hero checks, CO checks, <font color="#CC3333">Button bets</font>, Hero ?