$3/$6 hand

[PoorLawyer]

by BETS on third, does that mean you came in for a completion? I would probably raise 4th and hope to get it heads up, especially if you already showed aggression by coming in for the full bet.

On 5th, I would be troubled that you have a dead A and 4 and are drawing very thin if he does have the flush. But then his check on 6th tells me that your hand is good and a bet is in order.
I probably check the river but I think my river play is a bit weak after discussions on here the last couple weeks.
I dont know if I could lay down the river. He may be a donk and just backed into kings up, thinking they are good over the Qs on board and guessing you didnt have trip 4s with the dead 4 out there and not seeing anything else too scary out there.