MP is 38/16/3,8 with 56% foldtocbet and aggfact on streets 1,1/1,9/3,2
he plays a lot of hours at these tables but it's the first spot of this kind

turn line? river line?

with no blockers i think its a fold. Its also very very reasonable that he would play Asxs this way almost always.

check turn it's ok?
river b/f?

i think the turn check is okay, i don't see much value in a river bet though, especially at these stakes.

The sizing isn't very bluffy which is why I think its a clear river fold. You're hand is obviously bluff catching, and if someone wanted to raise you here with the naked As they're almost always going to be potting it.

i like the turn check. if we bet its mostly for protection against str8 draws which we block so i think most the time we will be value owning ourselves and add the possibility of the dreaded c/r i think its a check. (does lead to some tricky river spots on blanks facing a lead tho)

id imagine villain leads most medium flushes on river and maybe c/c's the very small 1s. so he is a little bit polarised so our str8 is a gd bluff catcher.

that being said.....

the flop c/c is likely Axxx and str8 draws which we block 56xx which also doesnt c/r river. so i think hes pretty weighted towards Axxxss he may c/r Kxxxss vs our river sizing and the fact we checked the turn.

nMCnasty made a gd point about the river sizing. im happily folding this a probably not v betting unless villain is a spazz.

im betting turn to try n get him off A4/A3, i play the river the same if i checked turn, folding to check raise