English politeness is mostly optional decoration: 'pass the salt' and 'could you pass the salt' differ in warmth, not in grammar. Thai does not work that way. ครับ and ค่ะ are closer to a required agreement marker: the sentence is incomplete without one, and leaving it off does not read as casual, it reads as curt.
They mark you, not the person you are talking to. A man says ครับ to everyone; a woman says ค่ะ. They do not change with the listener, so there is nothing to calculate.
- ครับkʰráp
male speaker, all sentences
statement or question, it does not change
- ค่ะkʰâ
female speaker, statements
- คะkʰá
female speaker, questions
high tone for a question, falling for a statement: the one thing to keep straight
What it costs to skip
Foreigners drop these constantly, and Thais forgive it instantly because you are foreign. That forgiveness is the trap: nobody will tell you, so the habit never gets corrected, and it will still be there in month six.
Attach it to the sentence from week one, not as a word you remember to add but as part of the sentence's shape. Say the whole thing as one unit, and resist the French pull to stress the last syllable, because that stress will land on the particle and distort it.