Negate past one time actions in Thai with “mâi dâai”

To negate a one-time action that wasn’t done, don’t use ไม่ (mâi) + verb. Instead, use ไม่ได้ (mâi dâai) + verb.

For example:

I didn’t go to school yesterday
ฉันไม่ได้ไปโรงเรียนเมื่อวาน
chăn mâi dâai bpai rohng riian mêuua waan.

“Not going to school yesterday” is a “one-time” action.

But if you want to say that in general you don’t go to school whether in the past or in the present you would use ไม่ (mâi) + verb.

For example:

I don’t go to school/I didn’t used to go to school.
ฉันไม่ไปโรงเรียน
chăn mâi bpai rohng riian

“Not going to school” in general is not a “one-time” action. It’s a on going habit whether in the past or present depending on the context.

Important: don’t get confused with …ไม่ได้ (…mâi dâai) which means “cannot”. The one we are dealing with must be followed by a verb.

Contents

Structure
Examples
Common mistake 1
Common mistake 2
Common mistake 3
Common mistake 4

Structure

Use ไม่ได้ (mâi dâai) to negate one time past actions.

⭐️ ไม่ได้ (mâi dâai) + verb

Examples

ฉันไม่ได้ทำ chăn mâi dâai tam ➜ I didn't do it.
ทำไมไม่ได้ทำการบ้าน tam-mai mâi dâai tam gaan bâan ➜ Why didn't you do homework?
ทำไมคุณไม่ได้ช่วยเขา tam-mai kun mâi dâai chûuay kăo ➜ Why didn't you help him?
ฉันไม่ได้กินเค้กในตู้เย็น chăn mâi dâai gin kék nai dtôo yen ➜ I didn't eat the cake in the fridge.
ทำไมไม่ได้ไปโรงพยาบาล tam-mai mâi dâai bpai rohng pá-yaa-baan ➜ Why didn't you go to the hospital?
ทำไมไม่ได้มาอาทิตย์ก่อน tam-mai mâi dâai maa aa-tít gòn ➜ Why didn't you come last week?
เขาไม่ได้ดื่มเหล้าเมื่อคืน kăo mâi dâai dèum lâo mêuua keun ➜ He didn't drink alcohol last night.

Common mistake 1

A common mistake is using ไม่ (mâi) instead of ไม่ได้ (mâi dâai) to negate a one time action in the past.

Question เมื่อวานไปโรงเรียนหรือเปล่า mêuua waan bpai rohng riian rĕu bplào ➜ Did you go to school yesterday?
Wrong answer ❌ ไม่ไป mâi bpai 👉 ('mâi bpai' is like saying "I am not going")
Correct answer ✅ ไม่ได้ไป mâi dâai bpai 👉 (this one correctly means "didn't go") ➜ I didn't go.

Common mistake 2

Sometimes people want to say “why didn’t you…” using ทำไมไม่ (tam-mai mâi) + verb. ทำไมไม่ (tam-mai mâi) + verb means “why don’t you…”. ทำไมไม่ (tam-mai mâi) is not used to talk about the past, but instead, the present and future.

Translate this question Why didn't you go to school?
Wrong answer ❌ ทำไมไม่ไปโรงเรียน tam-mai mâi bpai rohng riian 👉 (with only 'mâi', the sentence means 'why don't...' ) ➜ Why don't you go to school?
Correct answer ✅ ทำไมไม่ได้ไปโรงเรียน tam-mai mâi dâai bpai rohng riian ➜ Why didn't you go to school?

Common mistake 3

When negating past habits, use ไม่ (mâi) + verb. Don’t use ไม่ได้ (mâi dâai) + verb.

Translate this question Why didn't you play games before but now you play?
Wrong answer ❌ ทำไมเมื่อก่อนไม่ได้เล่นเกมส์แต่ตอนนี้เล่น tam mai mêuua gòn mâi dâai lên gem dtàe dton-née lên 👉 ( "playing games" is a past habit not a one-time action )
Correct answer ✅ ทำไมเมื่อก่อนไม่เล่นเกมส์แต่ตอนนี้เล่น tam-mai mêuua gòn mâi lên gem dtàe dton-née lên ➜ Why didn't you play games before but now you play?

Common mistake 4

To understand, to hear, to know, to see, are not “active” actions. They are verbs but they are “passive” actions.

With these “passive” action verbs, just use ไม่ (mâi) to negate them, whether they are one-time actions, in the past, present, or future.

Wrong ❌ ไม่ได้เข้าใจ mâi dâai kâo jai 👉 (this is never correct)
Correct ✅ ไม่เข้าใจ mâi kâo jai ➜ I didn't understand, I don't understand, I can't understand, I couldn't understand
Wrong ❌ ไม่ได้ได้ยิน mâi dâai dâai yin 👉 (this is never correct)
Correct ✅ ไม่ได้ยิน mâi dâai yin ➜ I didn't hear, I don't hear, I can't hear, I couldn't hear
Wrong ❌ ไม่ได้รู้ mâi dâai róo 👉(this is never correct)
Correct ✅ ไม่รู้ mâi róo ➜ I didn't know, I don't know
Wrong ❌ ไม่ได้เห็น mâi dâai hĕn 👉(this is never correct)
Correct ✅ ไม่เห็น mâi hĕn ➜ I didn't see, I don't see, I couldn't see