This has two different usages:
- to put in
กาแฟใส่นม // kaafae sài nom
Coffee puts (lit.) milk = Coffee with milk
Credit pic: here
ชาไม่ใส่น้ำตาล // chaa mâi sài námtaan
Tea doesn’t put (lit.) sugar = Tea without sugar
(At least for me I don’t add sugar or honey in my camomile tea.)
ส้มตำไม่ใส่พริก // sôm tam mâi sài phrík
Papaya salad doesn’t put (lit.) chilli = Papaya salad without chilli (how can this be possible!)
Credit pic: here
- to put on, to wear
ใส่เสื้อ // sài seûa
To put on clothes
Credit pic: here
ใส่รองเท้า // sài rawng thaáo
To put on shoes
Credit pic: here
For this option, it is possible to use สวม//sǔam as well.
- เอา ___ ใส่ // ao ___ sài
เอาเสื้อใส่(ใน)กางเกง // ao seûa sài (nai) kaang kehng
To put (lit.) the shirt into the pants = To tuck your shirt into the pants
Credit pic: here
เอาข้าวใส่(ใน)กล่อง // ao khaâo sài (nai) klàwng
To put (lit.) rice into the (lunch) box
Credit pic: here
ใส่ใจ // sài jai
As we just learnt, ใจ means heart or mind. When you are doing something and you put your heart into it, it means that you pay attention or you simply bother. The opposite is true: ไม่ใส่ใจ//mâi sài jai means you don’t put your heart into it, and therefore you cannot be bothered to do something (properly). On top of this, ใส่ใจ // sài jai also means to be attentive (of course, when you are paying attention, you are attentive).
ใส่อารมณ์ // sài ahrom
อารมณ์ // ahrom means mood or emotion. When the emotion is added to your thought, the result of your thought (or action) can be affected. Hence, we always say:
ทำอะไรอย่าใส่ (หรือ ใช้) อารมณ์
Tham àrai yàh sài (OR chái) ahrom
Learn Thai with Kelly 
