The past tense form (and also past participle) of to think is glaringly ambiguous against the noun thought, suggesting that thought might be going on.

I humbly suggest the alternative thunk tank.

The bad grammar eliminates suspicions of thought and as a bonus, it rhymes with drunk tank.

"I thinked and thinked real hard and real long till I couldn' think a nuthin' I ain't already thunk. So I then I passed on the remainin' reckonin' on to the fine folks in the thunk tank."