Vilain is a reg and we have no history

***** Hand History for Game 4964747949 *****
$100.00 USD NL Texas Hold'em - Friday, August 28, 08:45:59 ET 2009
Table Lulusar0 (Real Money)
Seat 5 is the button
Seat 1: xxx ( $220.95 USD )
Seat 2: xxx ( $16.95 USD )
Seat 3: Hero ( $118.60 USD )
Seat 4: xxx ( $97.00 USD )
Seat 5: xxx ( $106.00 USD )
Seat 6: Vilain ( $102.00 USD )
Vilain posts small blind [$0.50 USD].
xxx posts big blind [$1.00 USD].
Dealt to Hero K A
** Dealing down cards **
xxx folds
Hero raises [$3.50 USD]
xxx folds
xxx folds
vilain calls [$3.00 USD]
xxx folds
** Dealing Flop ** 2 A9
vilain checks
hero bets [$5.00 USD]
vilain raises [$15.00 USD]
hero calls [$10.00 USD]
** Dealing Turn **7
vilain bets [$15.00 USD]
hero?

I call on the flop coz he's not representing much, on the turn
it's more complicated...
thoughts

on flop I think his range is 22/99/A9s sometimes AQ/AJ, also sometimes 33-88, and obviously bluffs like JTs/QJs/KJs/KQ.
Call is obviously std.

turn he bets so small I dont think he has a set/2pair here often at all.
To me it really looks like he turned a diamond draw and is trying to get there cheaply.
I think raising small or calling are both fine but I think raising small and folding to a shove + betting small on blank river is slightly better than just calling.

I keep calling.