I have my opponent at 18/14 although prior to this hand he was playing tighter and so far had been very straight forward. I've taken down a couple 3-way pots from him when he's checked to my button.

Routine fold?

PokerStars No-Limit Hold'em, $1.00 BB (5 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

Button ($19.80)
SB ($157.70)
Fnord ($195.15)
UTG ($91.75)
MP ($109.20)

Preflop: Fnord is BB with J, T.
3 folds, SB raises to $4, Fnord calls $3.

Flop: ($8) J, A, T (2 players)
SB checks, Fnord bets $5, SB raises to $18