This is a spot I have trouble folding. I am not sure what is correct.

PokerStars Zoom Hand #167465111212: Hold'em No Limit ($0.02/$0.05) -

6-max Seat #1 is the button
button: ($4.86 in chips)
SB: ($6.37 in chips)
BB: ($5 in chips)
UTG$5 in chips)
HERO: ($13.69 in chips)
CO: ($8.61 in chips)
SB: posts small blind $0.02
BB: posts big blind $0.05
*** HOLE CARDS ***
Dealt to Hero [Ks Ah]
UTG: folds
HERO: raises $0.10 to $0.15
CO: calls $0.15
Buttn: calls $0.15
SB: folds
BB: folds

Pot $0.50
*** FLOP *** [4s Ac 8c]
Hero: bets $0.15
CO: folds
Button: raises $0.25 to $0.40
Hero: calls $0.25

Pot $1.30
*** TURN *** [4s Ac 8c] [Ts]
Hero: checks
Button: bets $0.65
Hero: calls $0.65

*** RIVER *** [4s Ac 8c Ts] [As]
Hero: checks
Button: bets $2.51


At these stakes I can beat AJ, AQ, and missed flushes.

Think he has a lot of AJ, AQ and also like you say missed flushes so for me it is a call on the river. From time to time he would have like trips 8 or 10. But it should be profitable to make the call.