Want=อยากได้
Want~
[อยากได้] + noun
I want car.
อยากได้รถยนต์
Don't want~
[ไม่](negative) + [อยากได้] +noun
I don't want car.
ไม่อยากได้รถยนต์
When asking a question
Do you want a car?
อยากได้รถยนต์ไหม
difference in nuance
*[อยาก]=[want]*
[อยากได้] implies a strong desire for something that is difficult or impossible to obtain.
For example:
[I don't have any money right now, but someday I want a car.]
Need=เอา
Need~(something)
[เอา] + noun
I need this.
เอาอันนี้
Don't need~
[ไม่](negative) + [เอา] + noun
I need don't this.
ไม่เอาอันนี้
When asking a question
Do you need this?
เอาอันนี้ไหม
difference in nuance
*[เอา]=[need]*
[เอา] is used for things in front of you, or things that you could quickly obtain, particularly for things you are receiving/getting. It is commonly used when shopping or eating out.
For example, at a food stall.....
-food stall worker : "What will you get?" [เอาอะไร]
-customer : "I'll get this." [เอาอันนี้]
: "I don't need chili pepper." [ไม่เอาพริก]
