• The 24-hour system (นาฬิกายี่สิบสี่ชั่วโมง   [nā-li-kā yêe-sìp-seè chûa-moūng]) is strictly used for official documents, business hours, schedules, and transport tickets.
• It is written followed by นาฬิกา   [nā-li-kā] (o'clock) or the abbreviation น. (e.g., 19:00 น. is read สิบเก้านาฬิกา   [sìp-kâo nā-li-kā]).

The spoken six-hour clock (นาฬิกาหกชั่วโมง   [nā-li-kā hòk chûa-moūng]) is a traditional timekeeping system used in the Thai language alongside the official 24-hour clock.
Like other common systems, it counts twenty-four hours in a day, but divides the day into four quarters, counting six hours in each. Because the afternoon splits into two, five spoken markers cover the day.

• ตี   [dteē] for the latter half of nighttime (01:00 to 05:59)
• โมงเช้า   [moūng cháū] for the first half of daytime (06:00 to 11:59)
• บ่ายโมง   [bàāi moūng] for the first three hours of the afternoon (13:00 to 15:59)
• โมงเย็น   [moūng yen] for the last three hours of the afternoon (16:00 to 18:59)
• ทุ่ม   [tùm] for the first half of nighttime (19:00 to 23:59)

The formal written version (ระบบเวลาแบบเป็นทางการ   [rá-bòp way-laa bàep bpen thaang-gaan]) is not a separate clock: it uses different names for some hours, and still divides the day into the same four quarters. Many hours are the same or nearly the same. The clearest difference is in the morning, where the written form numbers the hours within each quarter, so 07:00 is โมงเช้า   [moūng cháū] (the first morning hour), not เจ็ดโมงเช้า   [jèt moūng cháū]. There are also extra names such as ย่ำรุ่ง   [yâm-rúng] (dawn), ย่ำค่ำ   [yâm-khâm] (dusk) and ยาม   [yaam] (night watch). Compare both versions in the table below.

When to Use Which Clock

• The 6-hour clock is used in spoken daily life.
• The 24-hour system (ending in นาฬิกา   [nā-li-kā] or น.) is strictly used for official, business, and transport schedules.
• The traditional formal system (such as ย่ำรุ่ง   [yâm-rúng] or ย่ำค่ำ   [yâm-khâm]) appears mainly in literature, royal news broadcasts, and historical contexts.

Noon & Midnight Exceptions

• 12:00 is called เที่ยง   [thîang] or เที่ยงวัน   [thîang-wan].
• 24:00 (00:00) is called เที่ยงคืน   [thîang-kheēn].
• They fall outside the standard 1–5 counting pattern.

Conversational Pitfalls & Shortcuts

• 13:00 is usually just บ่ายโมง   [bàāi moūng] (omitting "one").
• 19:00 starts counting at "one" again as หนึ่งทุ่ม   [neùng tûm].
• In fast speech, morning hours (07:00–09:00) often omit เช้า   [cháū].

Minutes & Half Hours

• Half past: add ครึ่ง   [khrêung] to the hour. บ่ายสองโมงครึ่ง   [bàāi sǒong moūng khrêung] = 2:30 PM, เที่ยงครึ่ง   [thîang khrêung] = 12:30, หนึ่งทุ่มครึ่ง   [neùng tûm khrêung] = 7:30 PM.
• Any other minutes: the hour, then the number, then นาที   [nā-thee]. So 9:20 is เก้าโมงยี่สิบนาที   [gâo moūng yêe-sìp nā-thee]. In fast speech นาที is dropped: เก้าโมงยี่สิบ   [gâo moūng yêe-sìp].
• Just past the hour: add กว่า   [gwàa], as in บ่ายสองโมงกว่า   [bàāi sǒong moūng gwàa] (a little after 2 PM), often doubled กว่า ๆ when you are being vague. เกือบ   [geùap] goes in front of a time that is nearly here: เกือบบ่ายสองโมง   [geùap bàāi sǒong moūng].
• Minutes before the hour: Thai usually just counts up, as in บ่ายโมงห้าสิบ   [bàāi moūng hâa-sìp] (1:50), or uses อีก   [èek] + minutes + the hour: อีกสิบนาทีบ่ายสองโมง   [èek sìp nā-thee bàāi sǒong moūng] (ten to 2).
• The 24-hour clock simply appends the minutes: 14:15 is สิบสี่นาฬิกาสิบห้านาที   [sìp-seè nā-li-kā sìp-hâa nā-thee].

Origins of the Names

• ตี   [dteē] ("to strike") originates from night watchmen beating wooden blocks or gongs.
• โมง   [moūng] is onomatopoeia for the high-pitched ringing sound of daytime gongs.
• ทุ่ม   [tûm] is onomatopoeia for the deep thump sound of large nighttime drums.

Alternative 1-to-5 Morning Count

• Besides standard clock numbers (e.g., แปดโมง   [pæ̀æt moūng] for 8:00), spoken Thai frequently counts morning hours sequentially from 1 to 5.
• 07:00 = 1st hour (โมงเช้า   [moūng cháū] or หนึ่งโมงเช้า   [neùng moūng cháū])
• 08:00 = 2nd hour (สองโมงเช้า   [sǒong moūng cháū], often shortened in speech to just สองโมง   [sǒong moūng])
• 09:00 = 3rd hour (สามโมงเช้า   [sǎam moūng cháū]), 10:00 = 4th hour (สี่โมงเช้า   [seè moūng cháū]), 11:00 = 5th hour (ห้าโมงเช้า   [hâa moūng cháū])
• Very common over phone calls, everyday casual speech, and regional dialects across Thailand.

Time Zone

• Thailand uses one time zone all year: Indochina Time (ICT), seven hours ahead of UTC (UTC+7), called เวลามาตรฐานไทย   [way-laa mâat-dtrà-thǎan thai] in Thai.
• There is no daylight saving time. The clocks never change, so the gap to countries that do shift theirs - much of Europe and North America - moves twice a year while Thai time stays put.

Asking the Time & Making Plans

• "What time is it?" is กี่โมงแล้ว   [gèe moūng láew] or ตอนนี้กี่โมง   [dton-née gèe moūng]. Broadcast / formal style: เวลาเท่าไร   [way-laa tâo-rai].
• "At what time?" uses กี่โมง   [gèe moūng] as the question word: ไปกี่โมง   [bpai gèe moūng] (what time do you leave?), เจอกันกี่โมงดี   [jer gan gèe moūng dee] (what time shall we meet?).
• "At" a clock time or a part of the day: put ตอน   [dton] in front. ตอนบ่ายสามโมง   [dton bàāi sǎam moūng] (at 3 PM), ตอนเที่ยง   [dton thîang] (at noon), ตอนเช้า   [dton cháū] (in the morning).
• Arranging to meet: นัด   [nát] is "to set up a meeting", as in นัดกันตอนหกโมงเย็น   [nát gan dton hòk moūng yen] (let's meet at 6 PM).
• "In" a length of time: อีก   [èek] + the duration. อีกครึ่งชั่วโมง   [èek khrêung chûa-moūng] (in half an hour), อีกสองชั่วโมง   [èek sǒong chûa-moūng] (in two hours).