How to not beat the donks or how to play like a numpty

Playing at Red32 in a Level 3 Rounders tourney. Its in the early stages and blinds are 15 and 30 and I have about 1450.

In the big blind with K 3 off.

Gets called round to me with three other players left in. Small blind folded.

Flop comes K K 5. I decide to check and under the gun bets the pot (135).

I flat call with one other and I now do the obvious thing and forget everything about what cards the others could have.

Turn comes down with a 7 - all rainbow and I check again. Under the gun bets 150 other folds and I flat call again.

River is a 10 and I check again - of course all the time I think Im winning.

Under the gun bets 250 I raise to 500 and he goes all in. He had just over 2000 before the start of the hand. Without even thinking I call.

What I should have was at least think about the call and folded. The only hand where somebody goes all in that I can beat is K 2. He definitely has some sort of hand. He bet on the flop, turn and river and went all in when I raised.

He turned over K 7 and Im out.

Bad luck, although you don't beat K2, your 3 doesn't play (KKKT7), so you split with K2,K3,K4,K6 but then you are also behind to 55 77 TT and K7 up

In hindsight when he bets on the river you call and hope, but hindsight is 20/20 and even when he 3bets... it is still very hard to fold trip K's here. I'm assuming this is a fr and especially early on, he could just be representing the K that he doesn't have.

Better luck next time