The correct form is "does he know." "Does he knows" is not correct.

In English, when using the auxiliary verb "do" in questions or negative statements with third-person singular subjects (he, she, it), the main verb remains in its base form (infinitive form) without the "s" ending.

Examples:

  • Correct: Does he know the answer?
  • Incorrect: Does he knows the answer?
  • Correct: She does not know the way.
  • Incorrect: She does not knows the way.

Example sentences

  1. Does he know how to play the guitar?
  2. Does she know where the nearest post office is?
  3. Does he know that you're coming to the party?
  4. Does she know the secret code to unlock the safe?
  5. Does he know the answer to the math problem?
  6. Does she know about the surprise birthday celebration?
  7. Does he know how much effort you put into this project?
  8. Does she know the reason behind the sudden change in plans?
  9. Does he know the way to the museum from here?
  10. Does she know why his car won't start?

Want to sound like a native speaker?

Engram’s AI-powered grammar checker makes your English sound like a native speaker’s, suggesting natural English expressions on top of fixing grammar, spelling, punctuation, word order, and vocabulary.

Free Grammar Checker
Check your grammar, spelling, punctuation, and word usage errors with Engram’s free online grammar checker using AI
Engram

Reference:

does
1. he/she/it form of do 2. he/she/it form of do 3. present simple of do, used…
Cambridge Dictionary

https://learnenglish.britishcouncil.org/grammar/english-grammar-reference/present-simple?page=3