กินข้าว

Yes, figuratively. If you say 'Let's go kin khao,' you can end up eating noodles. But if you are already at the stall, you'd say 'kin sen' (eat noodles).

Not to friends, but to elders or in formal writing, it's better to use 'than' or 'rap-pra-than'.

Say 'Kin laew' (already eaten) or 'Yang' (not yet).

It's a cultural way to show care. In the past, food security was the most important thing, so checking if someone ate was the ultimate sign of friendship.

'Kin' is used for both eating and drinking informally. 'Duem' is specifically for drinking and is more formal.

Yes! You can replace 'khao' with any food name: 'kin pizza', 'kin som tam', 'kin sushi'.

It literally means 'with rice' and refers to the side dishes or the main meal items that accompany the rice.

Yes, for 'rice'. If the tone changes, the meaning changes completely (e.g., 'Khao' rising tone means 'he/she').

No, Thai often drops the subject. Just 'Kin laew' is perfectly natural.

Yes, it's very vulgar. Only use it with friends you've known for years who use it with you first.

Use 'kin len' (eat for fun) or 'kin khanom' (eat sweets/snacks).

Yes, it's the standard across all regions, though local dialects might have their own variations.

Only if the interviewer invites you to lunch. Otherwise, stick to formal language.

Around 11:30 AM - 1:00 PM (lunch) and 6:00 PM - 8:00 PM (dinner).