What is the Thai term for "when"?

The term "เมื่อไหร่" (muea rai) specifically translates to "when" in Thai, making it the appropriate choice for expressing inquiries about time or specific occurrences. This phrase is commonly used in questions to ask about the timing of events, such as "When are you coming?" or "When does the meeting start?"

The other options refer to different concepts: "วันนี้" (wan nee) means "today," which indicates the current day, while "คืนนี้" (khuen nee) translates to "tonight," specifying a time period later in the day. Lastly, "เมื่อ" (muea) means "when," but it is typically used in a different grammatical context and does not carry the same question form as "เมื่อไหร่" (muea rai). Therefore, the phrase "เมื่อไหร่" is the correct term when asking about timing in a straightforward manner.