Each Thai term is followed by its RTGS romanization. Where a recording is available, select its speaker button to listen.
Why one Thai word has several spellings
You look up a Thai word in a textbook, then find a different spelling on a sign or in a message. Often, both spellings refer to the same word. They just use different ways of writing Thai sounds with Latin letters.
The greeting สวัสดี (Sawatdi) illustrates the difference. Its RTGS spelling appears in parentheses, followed by its recordings. You may also see the informal spellings sawasdee and sawadee, or the learner spelling sà-wàt-dii, which shows tones and the long final vowel.
Writing Thai with Latin letters is called romanization. Some spellings follow a defined system; others are personal or informal. Learn the system’s sound key before reading a spelling aloud, since the letters may work differently from ordinary English.
Check the Thai word: ค่ะ (Kha) and สวัสดี (Sawatdi) each have a standard Thai spelling. When two Latin spellings look different, compare the Thai script to see whether they refer to the same word.
Why Thai sounds are difficult to romanize
Thai script and English spelling represent sounds in different ways. Two differences matter immediately for learners:
1. Thai consonants do not map one to one to English letters
Thai has 44 consonant letters representing a smaller number of consonant sounds. Several letters may sound similar to an English learner, but their consonant class affects the tone rules. A Latin spelling usually leaves that information out.
2. Aspiration changes the sound
Thai distinguishes consonants with and without a puff of air, called aspiration. English speakers make both kinds of sound but do not usually treat them as different letters:
- Unaspirated “p” (ปอ ปลา (Po pla) ): A sound without a strong puff of air, similar to the “p” in the English word “spin”.
- Aspirated “p” (ผอ ผึ้ง (Pho phueng) , พอ พาน (Pho phan) , ภอ สำเภา (Pho samphao) ): A “p” with a puff of air, like the “p” in “pen”.
Romanization systems often add an h to mark aspiration. That is why you see ph, th, and kh.
Watch for “ph”: In Thai romanization, ph normally represents an aspirated p, not an f. This is why ภูเก็ต (Phuket) begins with a p sound.
RTGS: the (mostly) official system
The Royal Thai General System of Transcription (RTGS) is Thailand's official* transcription system. The UN geographical-names guidance sets out the rules used to transcribe Thai place names.
* = Technically, RTGS is supposed to be the official system for Thai place names, but it is not consistently applied.
You can encounter RTGS on maps and signs, alongside established spellings that differ from it. Do not assume that a person's passport spelling or a transport station's English name follows RTGS exactly. Use the spelling shown in the relevant document.
How RTGS works
RTGS transcribes pronunciation rather than substituting one Latin letter for each Thai letter. It omits tones and does not distinguish short from long vowels. The table separates familiar spellings from features you need to listen for:
Swipe sideways to see all columns.
| Thai Script, RTGS & Audio | Other Spellings You May See | Pronunciation Notes |
|---|---|---|
| สวัสดี (Sawatdi) | sawasdee, sawadee | Three syllables: low, low, mid tones; a long final vowel. |
| ขอบคุณ (Khop khun) | khob khun | The first syllable has a long vowel and low tone; the second has a short vowel and mid tone. The final consonant of the first syllable is an unreleased p. |
| ภูเก็ต (Phuket) | Phoo-ket | Two syllables: mid then low tone. The first vowel is long; the second is short. The name begins with an aspirated p. |
| เกาะ (Ko) | koh | “Island”: an unaspirated k, a short open o vowel, and a low tone. The syllable ends with a glottal stop. |
| เชียงใหม่ (Chiang Mai) | Chiangmai | Two syllables, not three: The first syllable has a vowel that glides within one syllable and a mid tone; the second has a low tone. |
The limitation of RTGS for learners
RTGS leaves out part of the pronunciation. You still need to learn the tone and vowel length, because those differences can change the word.
Standard Thai has five tones: low, mid, falling, high, and rising. The following words share one RTGS spelling: ใหม่ (Mai) (new, low tone), ไม้ (Mai) (wood, high tone), ไม่ (Mai) (not, falling tone), or ไหม้ (Mai) (burn, falling tone). Context and Thai spelling help identify the word; tones alone do not distinguish every pair.
Paiboon: a system for learners
The lesson cards offer a Paiboon option based on the learner notation used in Paiboon Publishing materials. It adds tone and vowel information that RTGS leaves out. Paiboon and the newer Paiboon+ have differences in their vowel symbols; check the key in the resource you are using.
Accent marks show tones, and doubled vowels often show length. In the table below, the greeting in the low-tone row has two low-tone syllables followed by a mid-tone syllable. The two female polite particles also appear here; the polite-particle guide explains when to use each one.
Swipe sideways to see all columns.
| Tone | Mark / Accent | Example (Thai, RTGS & Audio) | Paiboon |
|---|---|---|---|
| Mid Tone | No accent | ไป (Pai) (go) | bpai |
| Low Tone | Grave accent (`) | สวัสดี (Sawatdi) (hello) | sà-wàt-dii |
| Falling Tone | Circumflex (ˆ) | ค่ะ (Kha) (polite fem.) | kâ |
| High Tone | Acute accent (´) | คะ (Kha) (polite question) | ká |
| Rising Tone | Caron / Háček (ˇ) | ฉัน (Chan) (I / me, dictionary form) | chǎn |
Keep the consonant systems separate
- Consonants: Paiboon writes unaspirated ปอ ปลา (Po pla) and ตอ เต่า (To tao) as bp and dt, while its p and t are aspirated. Its g represents unaspirated กอ ไก่ (Ko kai) , while k represents aspirated consonants such as คอ ควาย (Kho khwai) . The paired letters bp and dt each represent one consonant sound.
- Vowel length: Long vowels are often written with double letters, as in kruu for ครู (Khru) . You will meet this word in the guide to Thai teacher titles.
- Tones: Accent marks indicate the tone of each syllable.
On the lesson cards: The Choose your preferences panel lets you show RTGS, Paiboon, both, or Thai script only. This changes the cards; the explanatory spellings in articles stay visible.
IPA: the International Phonetic Alphabet
IPA stands for the International Phonetic Alphabet. You may have seen it beside words in a dictionary. It is used to write down speech sounds across languages, using both familiar letters and special symbols. Each has a meaning in the IPA sound key, so English spelling rules will not always help you read it.
If you were hoping for an India Pale Ale, sorry. This IPA comes with homework.
Reading the symbols
- Aspiration: The raised ʰ means a puff of air. Compare unaspirated [p] with aspirated [pʰ]. The same mark appears in [tʰ] and [kʰ].
- Vowel length: [aː] is the long version of [a]. The symbol ː tells you to hold the vowel longer.
- Tones: Pitch marks can show how your voice moves through a syllable. One simplified notation for Thai uses ˧ for mid, ˨˩ for low, ˥˩ for falling, ˦˥ for high, and ˩˩˦ for rising. Exact pitch shapes vary between speakers, and dictionaries may use different conventions.
Try it with the word for teacher
Take ครู (Khru) , meaning “teacher.” In IPA, you can write it as [kʰruː˧]. The [kʰ] tells you to start with a puff of air, followed by [r] and a long [uː]. The final ˧ marks the mid tone. This is the same word written khru in RTGS and kruu in Paiboon.
When looking up words, you may see slashes, /…/, around a language’s sound categories, or square brackets, […], around a transcription of pronunciation. Some dictionaries use tone accents instead of pitch letters. Check the key in the dictionary you are using.
The official IPA chart is useful for looking up an unfamiliar symbol. For Thai examples, see the IPA guide on Slice of Thai. Read the symbols while listening to the word; hearing it will help you make sense of the notation.
Quick reference for RTGS Romanized Thai
The consonant examples below describe RTGS at the start of a syllable. They do not apply unchanged to Paiboon or to final consonants. The English comparisons are approximations.
For a name on a class list, ask the student to say it. Their English spelling may follow neither system. The guide to names and nicknames explains why a student may introduce themselves by a name that differs from the one on your list.
1. In RTGS, “h” can mark a puff of air
- K: Crisp, hard sound like the “k” in skin (Thai: กอ ไก่ (Ko kai) ).
- KH: Breathy puff of air like the “k” in kite (Thai: ขอ ไข่ (Kho khai) , คอ ควาย (Kho khwai) ).
- T: Crisp stop like the “t” in stop (Thai: ตอ เต่า (To tao) ).
- TH: Breathy puff like the “t” in top (Thai: ทอ ทหาร (Tho thahan) , ถอ ถุง (Tho thung) ). This is different from English “th” in think.
- P: Crisp stop like the “p” in spin (Thai: ปอ ปลา (Po pla) ).
- PH: Breathy puff like the “p” in pie (Thai: พอ พาน (Pho phan) , ผอ ผึ้ง (Pho phueng) ). This represents p with aspiration, not f.
2. Common vowel spellings
- RTGS i: Can represent a short or long vowel. In สวัสดี (Sawatdi) , the final vowel is long; its length comes from the Thai word, not the Latin letter.
- RTGS u: Also leaves vowel length unspecified. The learner spelling kruu makes the long vowel in ครู (Khru) explicit.
- RTGS ai: A vowel glide roughly like the sound in eye. An informal spelling ending in ay is not a reliable pronunciation rule.
3. Student nicknames may use personal spellings
Thai nicknames, ชื่อเล่น (Chue len) , often have personal Latin spellings. Examples you may meet include:
- พลอย (Phloi) (personal spelling Ploy), meaning “gemstone”
- แบงค์ (Baeng) / เบนซ์ (Ben) / เบียร์ (Bia) : (personal spellings Bank / Benz / Beer). Examples of nicknames drawn from foreign words or brand names.
- ฟ้า (Fa) (personal spelling Fah), meaning “sky,” with a long vowel
- เอิร์ธ (Oet) / ไอซ์ (Ai) / กอล์ฟ (Kop) : (personal spellings Earth / Ice / Golf). Nicknames based on English words; their Thai pronunciation may differ from the English one.
Practice with the script and sound together
Choose one lesson phrase and compare it romanizations. Notice what the tone marks and doubled vowels add, then listen when a recording is available. If a spelling seems ambiguous, check the Thai word in a dictionary that provides audio.
For the full sound keys, see the comparison of pronunciation systems by the Paiboon dictionary app developer