how to use attend to,intend to,concentrate on

[sirin malinil]

คือว่า เช้าๆเวลาส่งลูกจะบอกให้เค้าตั้งใจเรียนน่ะค่ะ

พอไปเปิดดิก เจอตั้ง3 คำ ใช้ยังงัยคะ

[David]

to concentrate is the intransitive form (i.e, it doesn't have an object).

e.g. "Please concentrate".

However, if you want to add more information, you to have to turn it into a transitive form (i.e. a verb that needs an object.)
We do this by forming the phrasal verb "to concentrate on".

"Please concentrate on your homework".

Note, you CANNOT say "Please concentrate your homework".

The meaning of "concentrate" above means to direct your mental power or effort. "Concentrate" also has another meaning - "to bring or come together in a large number".

e.g. "In the summer, animals often concentrate where there is water".

Ajarn Peter is correct therefore, when he says that adding "on" enables you add more information.

Hope this helps. If you are still unsure, tell me and I will try to explain it in another way.

Best
David

[May, แม่น้องเอินเอิน]

Big Thanks to both of you Ajarn Peter and Ajarn David