I mean this tax regulation seems uneven and it seems that people who have to pay taxes are people who deal with large amounts of money. Let's say a farmer in 1 harvest (3-4 month) earns $2000, he will remain tax free if not registered or he doesn't register it whereas an employee from the start is already registered with the taxpayer even though their monthly salary is $300. What do you think? I'm a little confused with this tax rule.
With this you could see the reason that it may be uneven and although that depends on government. Some government don't have better data of their citizens and because of that, it can't trace those who are suppose to remit tax money to government. So because they don't have such data, they are not strictly practicing tax compliance therefore some people exempt themselves. For example with what you mentioned, a farmer who does not have his or her data, farm registered with government, the government will find it difficult to locate and that is part of the reason. This is mostly the situation in third world countries. Those who pay taxes are those that are employed with the government because it is removed from source as income tax.