PokerStars Hand #217212509154: Hold'em No Limit ($0.15/$0.30 USD)

CO ($14.56 in chips)
BT: HERO ($34.97 in chips)
SB ($46.88 in chips)
BB ($30.66 in chips)
UTG: VILLAIN ($48.38 in chips)
MP ($83.32 in chips)

* HOLE CARDS
Dealt to cfesta23 [Qs Ks]
VILLAIN: raises $0.35 to $0.65
MP: folds
CO: folds
HERO: calls $0.65
SB: folds
BB: folds
FLOP [5c Kd Ad] Pot: $1.75
VILLAIN: bets $0.55
HERO: calls $0.55
TURN [5c Kd Ad] [Th] Pot: $2.85
VILLAIN: bets $2.03
HERO: calls $2.03
RIVER * [5c Kd Ad Th] [4h] Pot: $6.91
VILLAIN: bets $4.92
HERO folds?

Is this too soft a fold? I think against an unknown villain triple barrels with an Ace or complete air, and given villain is unknown im not sure how often he shows up with air so I just laid it down. Would a raise on the flop or turn have been a good play?