I'd just change one small thing  -  you edited one of Youtthasack's sentences:

Furthermore, lessons and experiences from those people can be very useful. Because they have tried massive procedures and measures when they are endeavoring to eradicating poverty before reaching their target.

I'd join the second sentence to avoid a fragment.

Furthermore, lessons and experiences from those people can be very useful because they have tried many programs and measures to eradicate poverty before reaching their target.

Watch out for sentences starting with 'because'!

Great work again. Much appreciated!

Word Choice

• Many countries obviously let others to come in → Many countries let others to come. (The word ‘obviously’ is not needed and here it sounds as if you are referring to something being discussed earlier or understood between you and the reader. Good for speaking, not for writing.)
• Many countries let others to come in and invest or launch many businesses and projects → Many countries allow foreign organizations and companies to launch businesses and projects or to invest in their economies. (Specify!)
• Necessary, inevitable → these mean the same in your sentence. What are you trying to say? Well spotted, Alison!
• the aids are really needed → foreign aid and investment are really needed
• researches → research (always singular)
• The financial aids → Financial aid (always singular)
• All would be very models for others to follow → All would be very good/useful/beneficial/etc models for others to follow.
• Building convenient schools costs a lot of money  well-designed? / efficient?  
• foreign aids are undeniable → foreign aid is essential Well spotted, Alison!
• assistances  assistance (singular)
• And the wealthy nations should provide them useful and fair assistances.  -  Youtthasack, don’t start sentences with 'And,' 'So,' 'For,' 'But,' 'Although,' or 'Because.'

 Organization: Thesis Sentence

• Those are the lack of knowledge, experience and budget. (This sounds like three things -  you said you were going to analyze two!)  Let’s make it less confusing!

Those are the lack of knowledge and experience and the lack of financial resources.

That is very useful for me, as am having essay test next month.

Financial support, in addition, is critical issue to run all progress. Take Laos PDR and Cambudia as example. They have to borrow a range of budget from others as they can not afford themselves. The financial aids will be used in various sectors such as infrastructural, educational, agricultural and health-care improvement ( all should be changed to noun——infrastructure, education, agriculture and healthcare. That is because you said sectors. It should be paralleled). Building convenient schools costs a lot of money, for example.

1、'Example' has been use in too many times; you could try 'instance'. 

2、'used' has also been used in several times. You could convert it into ' distributed '. They express the same meaning regarding to this sentence.

3、Again, the 'example' is too short——your last sentence. Here is my example.

For instance, constructing convenient schools could costs a great amount of money, simply due to the pricey teaching equipment. With no doubt, the school managements can impossibly afford to any advanced techniques without enough money. Therefore, they cannot offer their students the good study environment.

1、The low developed countries lack knowledge and experiences in development field ( eliminate! Because you have referenced 'development' in your intro). They need good experts, technical staff and researchers.  These people play an important role in country’s transformation. Good researches are required to run all projects, for example. (example could be more specific. lenthenning!)

1、Less developed countries are lack of knowledge and experience. They need technical experts and researchers since these people are playing an important role in country's transformation. For example,………………

2、Furthermore, lessons and experiences from those are very useful. They had used and tried many procedures and policies in pursuit of eradicating poverty until reaching the target. All would be very models for others to follow. ( this short sentence is very nice; I like it!) American, Japan and Australia are excellent examples to be learnt. (these sentences are all short sentences)

2、Furthermore, lessons and experiences from those people can be very useful. Because they have tried massive procedures and measures when they are endeavoring to eradicating poverty before reaching their target. All these would be the very models for others to follow.  Consider America, Japan and Australia, all of them are exellent examples to be learnt.

In conclusion, foreign aids are undeniable ( undeniable what )for least developed countries in terms of development ( development in poor countries or in rich countries? Although I know you mean in poor countries, I think you should express clear and more precise in terms of the structure of this sentence. Note! I am not 100% sure whether this suggestion is right or not)

In conclusion, foreign aids are undeniable important/crucial/significant/essential for less developed countries since they need development.

Many countries obviously let others to come in and invest or launch many businesses and projects. ( invest includes launching businesses projects.  ——Many developing countries often let foreigners come inside to invest.)

They claim that this is necessary in terms of their county’s development, while others think that this is inevitable.  ( this former sentence is expressing the same view as the later one. ——They think that this economic policy is inevitable for the sake of country's development while others think not.)

This essay will analyze two( you referenced 3 factors) fundamental points that show that the aids are really needed for the low income-earner states. Those are the lack of knowledge, experience and budget. ( This essay will analyze three fundamental points that show the aids are significant for the poor states, which are the lack of knowlege, experience and budget.)

The low developed countries lack knowledge and experiences in development field. They need good experts, technical staff and researchers.  These people play an important role in country’s transformation. Good researches are required to run all projects, for example. Furthermore, lessons and experiences from those are very useful. They had used and tried many procedures and policies in pursuit of eradicating poverty until reaching the target. All would be very models for others to follow. American, Japan and Australia are excellent examples to be learnt.  

Financial support, in addition, is critical issue to run all progress. Take Laos PDR and Cambudia as example. They have to borrow a range of budget from others as they can not afford themselves. The financial aids will be used in various sectors such as infrastructural, educational, agricultural and health-care improvement. Building convenient schools costs a lot of money, for example.

In conclusion, foreign aids are undeniable for least developed countries in terms of development. And the wealthy nations should provide them useful and fair assistances. 

236 words,

My assignment expects ≥ 200 words