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If you’ve been learning Thai for a while, you might have wondered:
“Why does this word have no vowel, but I still hear one when it’s spoken?”
Welcome to the world of reduced vowels, or in Thai, สระลดรูป (sà-rà lód rûup).
In our previous post, we explored transformed vowels (สระเปลี่ยนรูป – sà-rà bplìian rûup)—vowels that change their appearance when paired with a final consonant. In this post, we’ll uncover something even sneakier: vowels that vanish from writing entirely (or almost entirely), even though their sound is still there when you speak the word.
Is it a mystery to you? Let’s go through it step by step today.
Table of Contents
What Are Reduced Vowels (สระลดรูป - sà-rà lód rûup)?
In Thai, a reduced vowel is a sound of a vowel that doesn’t appear in full written form, partially or completely, but it’s still pronounced.
This change differs from transformed vowels, which change shape but are still visible in some form. With reduced vowels, some or all vowel forms just… disappear.
There are 4 common types of vowel reduction in Thai. Once you recognize these, you’ll read Thai with much more confidence and a lot less confusion.
The 4 Types of Thai Reduced Vowels
📢 Type 1: โอะ /o/ → Completely Hidden (e.g., กด, สด)
For this vowel, you can see that there are two vowel forms – one written in front of the initial consonant and the other one after the initial consonant.
When the short vowel /o/ (written โ + ะ) is followed by a final consonant, both vowel forms “โ” and “ะ” disappear.
Word | Sound | Full Vowel | Reduced Form |
กด | /gòt/ | โ + ะ | (nothing written) |
สด | /sòt/ | โ + ะ | (nothing written) |
ลด | /lót/ | โ + ะ | (nothing written) |
🔎 Tip: If you see a word with no vowel and a final consonant—and it sounds like /o/—you’re probably dealing with a reduced โอะ.
📢 Type 2: อัว /uua/ →" ั " Disappears, but "ว" Remains (e.g., ขวด, ปวด)
The vowel /uua/ is normally written with “ ั + ว + ด/ก/etc.”.
But when there’s a final consonant, the ” ั” (mái-hǎn-aa-gàat) disappears, leaving only “ว” to represent the sound.
Word | Sound | Full Vowel | Reduced Form |
ขวด | /kùuat/ | ั + ว | ว remains only |
ปวด | /bpùuat/ | ั + ว | ว remains only |
หมวด | /mùuat/ | ั + ว | ว remains only |
👀 Don’t be fooled— the form “ว” here isn’t just a consonant. It’s part of the vowel.
📢 เออ /ooe/ + ย → Second "อ" Disappears (e.g., เคย, เนย)
When the vowel /ooe/ (เออ) is used and ย is the final consonant, the second “อ” vanishes from the written form.
Only the “เ” remains as a vowel indicator.
Word | Sound | Full Vowel | Reduced Form |
เคย | /kooey/ | เ + ออ + ย | เ + ย |
เนย | /pooey/ | เ + ออ + ย | เ + ย |
เลย | /looey/ | เ + ออ + ย | เ + ย |
🎯 Think of this as a “half-visible vowel”—only the beginning “เ” is shown.
📢 ออ /aaw/ + ร → Second "อ" Disappears (e.g., พร, จร)
Similarly, when the vowel /aaw/ (ออ) is followed by ร as ending consonant, both “อ” vanish, while the full sound remains.
Word | Sound | Full Vowel | Reduced Form |
พร | /paawn/ | ออ + ร | – ร |
กร | /gaawn/ | ออ + ร | – ร |
ศร | /sǎawn/ | ออ + ร | – ร |
📌 The vowel looks like it’s gone, but the pronunciation is still long and clear.
🤲 Why Does This Matter for Thai Learners?
The Thai script and writing system differ in several ways from other languages. Not knowing these vowel transformation rules sometimes creates uncertainty for Thai learners, especially when the vowels you “hear” aren’t visible on the page.
Knowing these 4 patterns of vowel reduction helps you:
- Read correctly even when no vowel is shown
- Understand why some words look “incomplete”
- Improve your Thai spelling and pronunciation
- Avoid guessing the wrong vowel
Once you start seeing these hidden patterns, you’ll feel like you’ve unlocked a secret code.
🏋️♂️ Practice Time!
What is missing? and what rule type is the following?
Try figuring out which vowel has been reduced in each of these words:
Thai Word | Pronunciation | What’s Missing? | Rule Type |
ปด | /bpòt/ | ?? | Type ?? |
หวด | /hùuat/ | ?? | Type ?? |
เมย | /mooey/ | ?? | Type ?? |
จร | /jaawn/ | ?? | Type ?? |
Let’s have a look at the answers:
Thai Word | Pronunciation | What’s Missing? | Rule Type |
ปด | /bpòt/ | โ + ะ | Type 1 |
หวด | /hùuat/ | ั (mái-hǎn-aa-gàat) | Type 2 |
เมย | /mooey/ | อ (second) | Type 3 |
จร | /jaawn/ | อ (second) | Type 4 |
How did you do? Now you’re thinking like a Thai reader!
Recap: The 4 Rules of Thai Reduced Vowels
Let’s wrap up:
- โอะ /o/ plus ending consonant – both forms disappear entirely when followed by a final consonant
- อัว /uua/ plus ending consonant – the ั form disappears, but ว stays
- เออ /ooe/ + ย – the second อ disappears
- ออ /aaw/ + ร – the second อ disappears
These are subtle, sneaky, but super important. Keep an eye (and ear!) out for them as you read Thai.
In case you are interested in learning more about the transformation of Thai vowels, you can read our blog below:
📰 Blog: Form-changing Vowels in Thai
or learning about Thai scripts with the following video clip:
🎞️ YouTube:
Read & Write Thai Tutorial: เนย (สระเอ หรือ สระเออ?)
But if you want to learn how to read and write Thai scripts systematically, step-by-steply, we encourage you to check out our BananaThai’s Ultimate Thai Reading course.
The course is an ultimate guide to helping you master Thai reading effortlessly. We simplified complicated Thai rules to six easy-to-follow chapters with thirty lessons.
📞 Contact our team or book a private Thai lesson at lesson@bananathaischool.com. We are happy to help you get started easily.
